How Coral Reefs Build Themselves: Reading Answers & Explanations
IELTS Reading practice test · 14 questionsAcademicmedium
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About this passage
The passage opens: “Scattered through the warm, shallow seas of the tropics lie some of the richest and most colourful habitats on the whole of the Earth. Coral reefs cover only a tiny fraction of the ocean floor, yet they shelter a quarter of all the kinds of creature that live in the sea, and for this reason they are often called the…”
- Passage length: about 656 words
- Questions: 14
- Question types: Matching Information, Summary Completion, True / False / Not Given
“How Coral Reefs Build Themselves” is an original IELTS-style practice passage written by IELTS-Bank. It is not taken from an official IELTS or Cambridge test, so these answers only apply to our version.
Answer key at a glance
How Coral Reefs Build Themselves answers with explanations
Questions 1–6: Matching Information
The passage has six paragraphs, A-F. Which paragraph contains the following information? Write the correct letter, A-F.
- A. Paragraph A
- B. Paragraph B
- C. Paragraph C
- D. Paragraph D
- E. Paragraph E
- F. Paragraph F
- 1
the name of the tiny animals that build a reef
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Answer: Paragraph B
Why: This is the part of the passage that supports Paragraph B.
Evidence · Paragraph B “The builders are small, soft-bodied animals called polyps”
- 2
a comparison between reefs and a habitat found on land
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Answer: Paragraph A
Why: This is the part of the passage that supports Paragraph A.
Evidence · Paragraph A “…for this reason they are often called the rainforests of the ocean.”
- 3
the water conditions that a reef requires in order to grow
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Answer: Paragraph D
Why: This is the part of the passage that supports Paragraph D.
Evidence · Paragraph D “The water must be warm, clear and shallow enough for light to reach the coral”
- 4
the ways in which reefs benefit people and coastlines
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Answer: Paragraph F
Why: This is the part of the passage that supports Paragraph F.
Evidence · Paragraph F “They act as natural breakwaters, absorbing the force of the waves and so protecting low-lying coasts”
- 5
what happens to coral when it loses its algae
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Answer: Paragraph E
Why: This is the part of the passage that supports Paragraph E.
Evidence · Paragraph E “…the coral becomes stressed and drives out the algae that live within it. Robbed of its colourful partners, the coral turns a ghostly white”
- 6
the exchange of benefits between the coral and the algae
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Answer: Paragraph C
Why: This is the part of the passage that supports Paragraph C.
Evidence · Paragraph C “…they pass much of that food to the coral that houses them; in return the coral gives the algae a safe place to live”
Questions 7–10: Summary Completion
Complete the summary below.
Complete the summary using NO MORE THAN TWO WORDS from the passage for each answer. Each tiny polyp draws minerals from the seawater and builds a hard, protective cup of (7) ______ around its body. Living inside the tissues of every polyp are vast numbers of microscopic (8) ______ , which capture sunlight to make food and share it with the coral. This partnership is easily upset: if the water grows too (9) ______ and stays that way for too long, the coral drives out its partners in an event called (10) ______ , turning a ghostly white and losing its chief source of food.
- 7
Each tiny polyp draws minerals from the seawater and builds a hard, protective cup of ______ around its body.(max 2 words)
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Answer: limestone
Why: The answer “limestone” is taken from this sentence — copy the word(s) exactly as they appear. It fits the 2-word limit.
Evidence · Paragraph B “…uses them to build a hard, protective cup of limestone about its own body.”
- 8
Living inside the tissues of every polyp are vast numbers of microscopic ______ , which capture sunlight to make food and share it with the coral.(max 2 words)
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Answer: algae
Why: The answer “algae” is taken from this sentence — copy the word(s) exactly as they appear. It fits the 2-word limit.
Evidence · Paragraph C “Living inside the tissues of each polyp are enormous numbers of microscopic algae”
- 9
This partnership is easily upset: if the water grows too ______ and stays that way for too long, the coral drives out its partners in an event called ______ , turning a ghostly white and losing its chief source of food.(max 2 words)
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Answer: warm
Why: The answer “warm” is taken from this sentence — copy the word(s) exactly as they appear. It fits the 2-word limit.
Evidence · Paragraph E “When the surrounding water grows too warm and stays warm for too long, the coral becomes stressed and drives out the algae”
- 10
This partnership is easily upset: if the water grows too ______ and stays that way for too long, the coral drives out its partners in an event called ______ , turning a ghostly white and losing its chief source of food.(max 2 words)
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Answer: bleaching
Why: The answer “bleaching” is taken from this sentence — copy the word(s) exactly as they appear. It fits the 2-word limit.
Evidence · Paragraph E “…an event known as bleaching.”
Questions 11–14: True / False / Not Given
Do the following statements agree with the information given in the passage? Write TRUE if the statement agrees, FALSE if it contradicts, or NOT GIVEN if there is no information.
- 11
A coral reef is built by many tiny animals rather than by a single large creature.
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Answer: TRUE
Why: This sentence confirms the statement, so the answer is TRUE.
Evidence · Paragraph A “…the whole vast structure is the work of animals no bigger than a fingernail.”
- 12
The algae living inside coral provide it with food and much of its colour.
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Answer: TRUE
Why: This sentence confirms the statement, so the answer is TRUE.
Evidence · Paragraph C “…they pass much of that food to the coral that houses them ... The algae also lend the coral much of its brilliant colour.”
- 13
Coral reefs can grow in deep water where no sunlight reaches.
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Answer: FALSE
Why: This sentence directly contradicts the statement, so the answer is FALSE.
Evidence · Paragraph D “…reefs are found only in the sunlit shallows of tropical seas and never in cold or deep water.”
- 14
Coral reefs attract more tourists than any other natural feature on Earth.
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Answer: NOT GIVEN
Why: The statement claims that coral reefs attract more tourists than any other natural feature, but the passage never confirms or denies this, only mentioning that reefs draw visitors supporting coastal communities.
Closest related text · Paragraph F “And they draw visitors from around the world, supporting the livelihoods of many coastal communities.”
Estimated band score for this test
Your raw score out of 14 scaled to the 40-question IELTS Reading (Academic) conversion table. This is the same estimate the practice page shows after you submit. A single passage is a small sample, so treat it as a guide.
| Correct answers | Estimated band |
|---|---|
| 14 / 14 | 9.0 |
| 13 / 14 | 8.5 |
| 12 / 14 | 7.5 |
| 11 / 14 | 7.0 |
| 10 / 14 | 6.5 |
| 8–9 / 14 | 6.0 |
| 7 / 14 | 5.5 |
| 6 / 14 | 5.0 |
| 5 / 14 | 4.5 |
| 4 / 14 | 4.0 |
| 3 / 14 | 3.5 |
| 2 / 14 | 3.0 |
| 1 / 14 | 2.0 |
| 0 / 14 | 0.0 |
Full-test score? Use the IELTS band calculator.
Tips for the question types in this test
Matching Information
- Read each statement and identify exactly what kind of information you are looking for — a reason, a result, an example, a definition, a contrast.
- Note that the statements do NOT follow paragraph order, so treat each one as an independent search.
Common trap: Assuming the questions run in order — they do not, which makes linear reading inefficient.
Full Matching Information strategySummary Completion
- Read the full summary first and identify which passage section it covers.
- Predict the grammar and meaning required in every blank.
Common trap: Choosing an option only because it repeats a passage word.
Full Summary Completion strategyTrue / False / Not Given
- Read the statement first and underline the key idea, especially any qualifiers like "all", "only", "never", "always", "more than" or dates and numbers.
- Because the questions follow the order of the passage, scan for the paragraph that deals with the same topic rather than re-reading everything.
Common trap: Confusing "False" with "Not Given": choose False only when the passage actively contradicts the statement; if the passage is silent, it is Not Given.
Full True / False / Not Given strategyPractise “How Coral Reefs Build Themselves” under exam conditions
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