​8. Sentence Completion – 10 Questions from One Text

Reading Passage

The Wonders of the Solar System

Our solar system is a vast and fascinating place, consisting of the Sun, eight planets, numerous moons, asteroids, comets, and other celestial bodies. Each planet and moon has its own unique characteristics, and scientists continue to make new discoveries that challenge our understanding of how the solar system formed and evolved.

Mercury is the closest planet to the Sun and also the smallest. It has a heavily cratered surface, similar to Earth's Moon, because it lacks a substantial atmosphere to burn up incoming meteoroids. Temperatures on Mercury vary dramatically, ranging from over 400°C on the sunlit side to -180°C on the dark side. Despite being closest to the Sun, Mercury is not the hottest planet; that distinction belongs to Venus.

Venus is often called Earth's twin because it is similar in size and composition. However, its conditions could hardly be more different from Earth. Venus has a thick atmosphere composed mainly of carbon dioxide, with clouds of sulfuric acid. This creates an extreme greenhouse effect, making Venus the hottest planet in the solar system, with surface temperatures hot enough to melt lead. The atmospheric pressure on Venus is about 90 times that of Earth, equivalent to being nearly a kilometer underwater.

Earth, our home planet, is unique in the solar system for having liquid water on its surface and an atmosphere rich in oxygen. These conditions have allowed life to flourish. Earth has one large moon, which stabilizes our planet's rotation and causes the ocean tides. The Moon is gradually moving away from Earth at a rate of about 3.8 centimeters per year.

Mars, the red planet, gets its color from iron oxide, or rust, on its surface. It has the largest volcano in the solar system, Olympus Mons, which is nearly three times the height of Mount Everest. Mars also has evidence of ancient river valleys and lake beds, suggesting that liquid water once flowed on its surface. Today, water exists on Mars primarily as ice at the polar caps and possibly as liquid brines underground. Several rovers are currently exploring Mars, searching for signs of past microbial life.

Jupiter is by far the largest planet in our solar system, with a mass more than twice that of all other planets combined. It is a gas giant, meaning it has no solid surface. Jupiter's most famous feature is the Great Red Spot, a massive storm larger than Earth that has been raging for at least 400 years. Jupiter has at least 79 moons, including four large ones discovered by Galileo: Io, Europa, Ganymede, and Callisto. Europa is of particular interest to scientists because it likely has a subsurface ocean that could harbor life.

Saturn is best known for its spectacular ring system, composed primarily of ice particles with a smaller amount of rocky debris and dust. The rings are extremely thin, only about 10 meters thick in places, but they stretch nearly 300,000 kilometers across. Like Jupiter, Saturn is a gas giant and has over 80 moons. Its largest moon, Titan, has a thick atmosphere and liquid methane lakes on its surface, making it one of the most Earth-like worlds in the solar system, though extremely cold.

Uranus and Neptune are the ice giants of the outer solar system. Uranus is unique because it rotates on its side, likely due to a massive collision early in its history. This gives it extreme seasonal variations, with each pole experiencing 42 years of continuous sunlight followed by 42 years of darkness. Neptune, the farthest planet from the Sun, has the strongest winds in the solar system, reaching speeds of over 2,000 kilometers per hour. Both planets have faint ring systems and numerous moons.

Beyond Neptune lies the Kuiper Belt, a region of icy bodies including dwarf planets like Pluto. Pluto was once considered the ninth planet but was reclassified as a dwarf planet in 2006 when astronomers realized it was just one of many similar objects in this region. The New Horizons spacecraft flew past Pluto in 2015, revealing a surprisingly complex world with mountains, glaciers, and a thin atmosphere.

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Questions 1-10

Complete the sentences below.

Choose NO MORE THAN TWO WORDS from the passage for each answer.

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Question 1

Mercury has a heavily cratered surface because it lacks a substantial __________ .

🔑 Keywords: Mercury, heavily cratered surface, lacks, substantial

🔍 Scan the text for: why Mercury has many craters

📖 The text says in Paragraph 2: "It has a heavily cratered surface, similar to Earth's Moon, because it lacks a substantial atmosphere to burn up incoming meteoroids."

📝 Analysis: The reason is lack of atmosphere. The sentence needs what Mercury lacks. "Atmosphere" is the word, but the text says "substantial atmosphere" - the question already includes "substantial" so we need the noun that follows.

✅ Answer: atmosphere

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Question 2

Venus has a thick atmosphere composed mainly of __________ .

🔑 Keywords: Venus, thick atmosphere, composed mainly of

🔍 Scan the text for: composition of Venus's atmosphere

📖 The text says in Paragraph 3: "Venus has a thick atmosphere composed mainly of carbon dioxide."

📝 Analysis: The main component is carbon dioxide. This is two words.

✅ Answer: carbon dioxide

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Question 3

The atmospheric pressure on Venus is about 90 times that of Earth, equivalent to being nearly a kilometer __________ .

🔑 Keywords: atmospheric pressure, Venus, 90 times Earth, equivalent to, kilometer

🔍 Scan the text for: what the pressure on Venus is equivalent to

📖 The text says in Paragraph 3: "The atmospheric pressure on Venus is about 90 times that of Earth, equivalent to being nearly a kilometer underwater."

📝 Analysis: The pressure is like being underwater. The sentence needs the location. "Underwater" is one word.

✅ Answer: underwater

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Question 4

Earth's moon stabilizes our planet's rotation and causes the ocean __________ .

🔑 Keywords: Earth's moon, stabilizes rotation, causes, ocean

🔍 Scan the text for: what the moon causes in the oceans

📖 The text says in Paragraph 4: "Earth has one large moon, which stabilizes our planet's rotation and causes the ocean tides."

📝 Analysis: The moon causes tides. "Ocean tides" is two words, but the question already has "ocean" so we need the second word.

✅ Answer: tides

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Question 5

Mars gets its red color from iron oxide, or __________ , on its surface.

🔑 Keywords: Mars, red color, iron oxide, or, on its surface

🔍 Scan the text for: another name for iron oxide

📖 The text says in Paragraph 5: "Mars, the red planet, gets its color from iron oxide, or rust, on its surface."

📝 Analysis: Iron oxide is also called rust. The sentence structure "iron oxide, or ___" indicates we need the alternative name.

✅ Answer: rust

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Question 6

Olympus Mons on Mars is nearly three times the height of __________ .

🔑 Keywords: Olympus Mons, Mars, nearly three times, height of

🔍 Scan the text for: what Olympus Mons is compared to in height

📖 The text says in Paragraph 5: "Olympus Mons, which is nearly three times the height of Mount Everest."

📝 Analysis: It is compared to Mount Everest. This is two words (proper name).

✅ Answer: Mount Everest

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Question 7

Jupiter's most famous feature is the Great Red Spot, a massive storm that has been raging for at least __________ years.

🔑 Keywords: Jupiter, Great Red Spot, massive storm, raging for, at least, years

🔍 Scan the text for: how long the Great Red Spot has existed

📖 The text says in Paragraph 6: "Jupiter's most famous feature is the Great Red Spot, a massive storm larger than Earth that has been raging for at least 400 years."

📝 Analysis: The storm has raged for 400 years. The number is the answer.

✅ Answer: 400

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Question 8

Saturn's rings are composed primarily of __________ with some rocky debris and dust.

🔑 Keywords: Saturn's rings, composed primarily of, with some rocky debris and dust

🔍 Scan the text for: main component of Saturn's rings

📖 The text says in Paragraph 7: "Saturn is best known for its spectacular ring system, composed primarily of ice particles with a smaller amount of rocky debris and dust."

📝 Analysis: The rings are made of ice particles. The question asks for the primary component. "Ice particles" is two words.

✅ Answer: ice particles

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Question 9

Uranus rotates on its side, likely due to a massive __________ early in its history.

🔑 Keywords: Uranus, rotates on its side, likely due to, massive, early in its history

🔍 Scan the text for: what caused Uranus to rotate on its side

📖 The text says in Paragraph 8: "Uranus is unique because it rotates on its side, likely due to a massive collision early in its history."

📝 Analysis: The cause was a massive collision. The sentence needs the event. "Collision" is one word.

✅ Answer: collision

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Question 10

Pluto was reclassified as a dwarf planet in 2006 because it was just one of many similar objects in the __________ .

🔑 Keywords: Pluto, reclassified, dwarf planet, 2006, one of many similar objects in the

🔍 Scan the text for: where Pluto is located and why it was reclassified

📖 The text says in Paragraph 9: "Pluto was once considered the ninth planet but was reclassified as a dwarf planet in 2006 when astronomers realized it was just one of many similar objects in this region. Beyond Neptune lies the Kuiper Belt, a region of icy bodies including dwarf planets like Pluto."

📝 Analysis: Pluto is in the Kuiper Belt, which contains many similar objects. The region is called the Kuiper Belt. This is two words (proper name).

✅ Answer: Kuiper Belt

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Key Tips for Sentence Completion

✅ Read the incomplete sentence carefully and predict what type of word is missing (noun, number, etc.)

✅ Identify keywords around the blank to help locate the answer in the text

✅ Scan the passage for those keywords or their synonyms

✅ Pay close attention to the word limit (NO MORE THAN TWO WORDS)

✅ Copy words exactly as they appear in the passage

✅ Check that your answer makes grammatical sense in the sentence

✅ Numbers and proper names count as words

⚠️ Common mistake: Writing more than the allowed number of words

⚠️ Common mistake: Changing the form of the word (e.g., plural to singular)

⚠️ Common mistake: Choosing words that appear near the keywords but don't actually answer the question

⚠️ Common mistake: Not noticing that the answer might be a number or date

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8. Sentence Completion – 10 Questions from One Text (Example 2)

Reading Passage

The Great Barrier Reef

The Great Barrier Reef is one of the most spectacular natural wonders on Earth. Located off the coast of Queensland in northeastern Australia, it is the largest coral reef system in the world, stretching over 2,300 kilometers and covering an area of approximately 344,000 square kilometers. So vast is the reef that it can be seen from outer space.

The reef is not a single structure but a complex ecosystem composed of nearly 3,000 individual reefs and about 900 islands. It is home to an extraordinary diversity of marine life, including over 1,500 species of fish, 400 species of coral, 4,000 species of mollusks, and numerous sea turtles, dolphins, and whales. This biological richness led to the reef being designated a UNESCO World Heritage Site in 1981.

The coral polyps that build the reef are tiny, soft-bodied organisms related to sea anemones. Each polyp secretes a hard calcium carbonate skeleton that forms the structure of the reef. Thousands of genetically identical polyps living together form a coral colony. The polyps have a symbiotic relationship with microscopic algae called zooxanthellae that live inside their tissues. The algae perform photosynthesis, providing the polyps with food and oxygen, while the polyps provide the algae with carbon dioxide and protection. This relationship is essential for reef growth, as the algae also help the polyps produce their calcium carbonate skeletons more rapidly.

The Great Barrier Reef has been shaped by geological forces over millions of years. The current reef structure began growing about 20,000 years ago when sea levels rose after the last ice age. As the ocean waters rose, coral colonies grew upward, building upon older, submerged reefs. The reef continues to evolve today, though at a much slower rate, with coral growth averaging just one to three centimeters per year.

Indigenous Australian peoples have lived in the region for at least 40,000 years and have deep cultural connections to the reef. More than 70 traditional owner groups maintain ongoing relationships with the reef and its islands, using its resources for food, ceremony, and trade. Their knowledge of the reef's ecosystems, accumulated over millennia, is increasingly recognized as valuable for modern conservation efforts.

European exploration of the reef began in 1770 when Captain James Cook's ship, the Endeavour, ran aground on it. Cook and his crew spent nearly seven weeks repairing the vessel on the banks of a river that Cook later named the Endeavour River. Subsequent European settlement brought new pressures to the reef, including fishing, shell collecting, and later, tourism and coastal development.

Today, the Great Barrier Reef faces unprecedented threats. Climate change is the most serious danger, causing rising ocean temperatures that lead to coral bleaching. When water becomes too warm, corals expel their symbiotic algae, turning white and becoming vulnerable to disease and death. Major bleaching events occurred in 1998, 2002, 2016, 2017, and 2020, with some areas losing more than half their coral cover. Ocean acidification, also caused by increased carbon dioxide absorption, makes it harder for corals to build their skeletons.

Other threats include water pollution from agricultural runoff, which carries sediments, nutrients, and pesticides onto the reef. Outbreaks of crown-of-thorns starfish, which feed on coral polyps, have devastated large areas. Coastal development and overfishing add additional pressures. The cumulative effect of these threats has led scientists to warn that the reef's ecosystem may be approaching a tipping point.

Extensive conservation efforts are underway to protect the reef. The Australian government's Reef 2050 Plan, first introduced in 2015, sets out a comprehensive framework for improving water quality, controlling crown-of-thorns starfish, and restoring damaged areas. Research institutions are developing heat-resistant coral strains that might survive warmer oceans. Marine protected areas restrict fishing and other activities in sensitive zones. International cooperation on climate change remains critical, as local measures alone cannot address the fundamental threat of rising temperatures.

Despite the challenges, the Great Barrier Reef retains remarkable resilience. Some damaged areas have shown recovery when conditions improve. Its immense scale and diversity mean that while parts may be degraded, others continue to thrive. The reef's future depends on urgent global action to reduce greenhouse gas emissions, combined with sustained local conservation efforts.

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Questions 1-10

Complete the sentences below.

Choose NO MORE THAN TWO WORDS from the passage for each answer.

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Question 1

The Great Barrier Reef is located off the coast of __________ in northeastern Australia.

🔑 Keywords: located off the coast of, northeastern Australia

🔍 Scan the text for: which Australian state or region the reef is off the coast of

📖 The text says in Paragraph 1: "Located off the coast of Queensland in northeastern Australia."

📝 Analysis: The reef is off the coast of Queensland. This is one word (proper name).

✅ Answer: Queensland

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Question 2

The reef is so large that it can be seen from __________ .

🔑 Keywords: so large, can be seen from

🔍 Scan the text for: where the reef is visible from

📖 The text says in Paragraph 1: "So vast is the reef that it can be seen from outer space."

📝 Analysis: The reef can be seen from outer space. This is two words.

✅ Answer: outer space

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Question 3

The reef was designated a UNESCO World Heritage Site in __________ .

🔑 Keywords: designated, UNESCO World Heritage Site, in

🔍 Scan the text for: the year the reef became a World Heritage Site

📖 The text says in Paragraph 2: "This biological richness led to the reef being designated a UNESCO World Heritage Site in 1981."

📝 Analysis: The year is 1981. This is a number (one word in IELTS counting).

✅ Answer: 1981

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Question 4

Coral polyps have a symbiotic relationship with microscopic algae called __________ .

🔑 Keywords: coral polyps, symbiotic relationship, microscopic algae called

🔍 Scan the text for: the name of the algae that live in coral polyps

📖 The text says in Paragraph 3: "The polyps have a symbiotic relationship with microscopic algae called zooxanthellae."

📝 Analysis: The algae are called zooxanthellae. This is one word (scientific name).

✅ Answer: zooxanthellae

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Question 5

The current reef structure began growing about 20,000 years ago when __________ rose after the last ice age.

🔑 Keywords: current reef structure, began growing, 20,000 years ago, when, rose

🔍 Scan the text for: what rose after the last ice age

📖 The text says in Paragraph 4: "The current reef structure began growing about 20,000 years ago when sea levels rose after the last ice age."

📝 Analysis: Sea levels rose. The sentence needs what rose. "Sea levels" is two words.

✅ Answer: sea levels

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Question 6

Indigenous Australian peoples have lived in the region for at least __________ years.

🔑 Keywords: Indigenous Australian peoples, lived in region, at least, years

🔍 Scan the text for: how long Indigenous peoples have lived there

📖 The text says in Paragraph 5: "Indigenous Australian peoples have lived in the region for at least 40,000 years."

📝 Analysis: They have lived there for 40,000 years. The number is the answer.

✅ Answer: 40,000

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Question 7

Captain Cook's ship, the Endeavour, ran aground on the reef in __________ .

🔑 Keywords: Captain Cook's ship, Endeavour, ran aground, in

🔍 Scan the text for: the year the Endeavour ran aground

📖 The text says in Paragraph 6: "European exploration of the reef began in 1770 when Captain James Cook's ship, the Endeavour, ran aground on it."

📝 Analysis: The year is 1770. This is a number.

✅ Answer: 1770

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Question 8

When ocean temperatures rise too high, corals expel their symbiotic algae and turn white, a process known as __________ .

🔑 Keywords: ocean temperatures rise, corals expel algae, turn white, process known as

🔍 Scan the text for: the term for corals turning white

📖 The text says in Paragraph 7: "Climate change is the most serious danger, causing rising ocean temperatures that lead to coral bleaching. When water becomes too warm, corals expel their symbiotic algae, turning white."

📝 Analysis: The process is called coral bleaching. This is two words.

✅ Answer: coral bleaching

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Question 9

Outbreaks of __________ , which feed on coral polyps, have devastated large areas of the reef.

🔑 Keywords: outbreaks of, feed on coral polyps, devastated large areas

🔍 Scan the text for: the creature that eats coral polyps

📖 The text says in Paragraph 8: "Outbreaks of crown-of-thorns starfish, which feed on coral polyps, have devastated large areas."

📝 Analysis: The creature is crown-of-thorns starfish. This is three words, but the question asks for NO MORE THAN TWO WORDS. Let's check carefully: "crown-of-thorns starfish" is hyphenated. In IELTS, hyphenated words often count as one word. "Crown-of-thorns" is hyphenated, and "starfish" is separate. That would be two words: "crown-of-thorns" (one hyphenated word) and "starfish" (second word).

📝 But the text also refers to them simply as "crown-of-thorns starfish." The question might expect the full name. However, given the word limit, we need the shortest identifiable form. The text says "crown-of-thorns starfish" as the full name. "Crown-of-thorns" alone might not be sufficient because it's an adjective describing starfish.

📝 Let's see if the passage uses a shorter form elsewhere. It doesn't. In this case, "crown-of-thorns starfish" is the name, and it's three words if we count each part separately. But the hyphens mean "crown-of-thorns" is treated as one unit. So "crown-of-thorns starfish" = two words.

✅ Answer: crown-of-thorns starfish (counts as two words due to hyphenation)

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Question 10

The Australian government's __________ , first introduced in 2015, sets out a framework for protecting the reef.

🔑 Keywords: Australian government's, first introduced in 2015, sets out framework, protecting reef

🔍 Scan the text for: the name of the government plan

📖 The text says in Paragraph 9: "The Australian government's Reef 2050 Plan, first introduced in 2015, sets out a comprehensive framework for improving water quality."

📝 Analysis: The plan is called Reef 2050 Plan. This is three words. But "Reef 2050" might be considered as one unit + "Plan"? The question asks for NO MORE THAN TWO WORDS. Let's check: "Reef 2050 Plan" is three separate words. Is there a shorter way? The text refers to it as "Reef 2050 Plan" consistently. In IELTS, sometimes proper names can exceed the word limit if they are the exact answer, but the instruction is strict.

📝 Perhaps they expect "Reef 2050" as the name, since "Plan" is implied? But the text says "Reef 2050 Plan." Looking at the sentence structure: "The Australian government's __________ , first introduced in 2015" – the blank needs the name of the plan. The full name is "Reef 2050 Plan." That's three words.

📝 This is a common issue in IELTS. Sometimes they accept the full proper name even if it exceeds the word limit, but officially you must follow the instruction. Let's see if the passage mentions it elsewhere. It only appears once. Given the constraint, we might need to choose the most essential two words. "Reef 2050" identifies the plan, and "Plan" is a generic word. Perhaps "Reef 2050" is acceptable.

📝 In many IELTS answer keys, they would accept "Reef 2050" for this type of question when the full name exceeds the limit.

✅ Answer: Reef 2050 (two words)