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Coral reefs are underwater structures made from calcium carbonate sec
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12 Oct 2025, 11:19
12 Oct 2025, 11:19
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Question 1
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67% (01:53) correct
33% (02:53) wrong based on 3 sessions
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Question 2
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Question Stats:
25% (00:28) correct
75% (00:57) wrong based on 4 sessions
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Coral reefs are underwater structures made from calcium carbonate secreted by corals. Corals are colonies of tiny living animals found in marine waters containing few nutrients. Most coral reefs are built from stony corals, and are formed by polyps that live together in groups. The polyps secrete a hard carbonate exoskeleton which provides support and protection for the body of each polyp. Reefs grow best in warm, shallow, clear, sunny and agitated waters. Often called 'rainforests of the sea', coral reefs form some of the most diverse ecosystems on earth. Paradoxically, coral reefs flourish even though they are surrounded by ocean waters that provide few nutrients. They are most commonly found at shallow depths in tropical waters, but deep water and cold water corals also exist on smaller scales in other areas.
Coral reefs deliver ecosystem services to tourism, fisheries and shoreline protection. The annual global economic value of coral reefs has been estimated at $\$ 30$ billion. However, coral reefs are fragile ecosystems, partly because they are very sensitive to water temperature. They are under threat from climate change, ocean acidification, blast fishing, cyanide fishing for aquarium fish, overuse of reef resources, and harmful land-use practices, including urban and agricultural runoff and water pollution, which can harm reefs by encouraging excess algae growth.
Coral reefs deliver ecosystem services to tourism, fisheries and shoreline protection. The annual global economic value of coral reefs has been estimated at $\$ 30$ billion. However, coral reefs are fragile ecosystems, partly because they are very sensitive to water temperature. They are under threat from climate change, ocean acidification, blast fishing, cyanide fishing for aquarium fish, overuse of reef resources, and harmful land-use practices, including urban and agricultural runoff and water pollution, which can harm reefs by encouraging excess algae growth.
According to the passage, all of the following statements are true EXCEPT:
(A) Coral reefs are found only in shallow, clear and sunny waters.
(B) Absence of nutrients in ocean water does not deter coral reefs from flourishing.
(C) Coral reefs are endangered because of water contamination.
(D) Coral reefs do not occupy a vast part of the ocean surface.
(E) Ocean temperature is crucial for the survival of coral reefs.
The passage provides information that helps answer all of the following questions about coral reefs EXCEPT:
(A) How are coral reefs formed?
(B) What are the threats to coral reef systems?
(C) What are coral reefs called?
(D) What protects coral reefs?
(E) Where are coral reefs found?
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Coral reefs are underwater structures made from calcium carbonate sec
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08 Nov 2025, 14:34
08 Nov 2025, 14:34
Expert Reply
Question 1
According to the passage, all of the following statements are true EXCEPT:
(A) Coral reefs are found only in shallow, clear and sunny waters.
Explanation:
- (A) False: The passage states that reefs "grow best in warm, shallow, clear, sunny and agitated waters," but then immediately notes the exception: "...deep water and cold water corals also exist on smaller scales in other areas." This contradicts the assertion that they are found only in shallow water.
- (B) True: The passage notes the "Paradoxically" that reefs "flourish even though they are surrounded by ocean waters that provide few nutrients."
- (C) True: The passage lists "urban and agricultural runoff and water pollution" as threats, which are forms of water contamination.
- (D) True: The passage says deep and cold water corals exist "on smaller scales," and that reefs are "most commonly found at shallow depths," implying they do not occupy a vast part of the entire ocean surface.
- (E) True: The passage states reefs are "very sensitive to water temperature" and are under threat from "climate change," indicating temperature is crucial for their survival.
According to the passage, all of the following statements are true EXCEPT:
(A) Coral reefs are found only in shallow, clear and sunny waters.
Explanation:
- (A) False: The passage states that reefs "grow best in warm, shallow, clear, sunny and agitated waters," but then immediately notes the exception: "...deep water and cold water corals also exist on smaller scales in other areas." This contradicts the assertion that they are found only in shallow water.
- (B) True: The passage notes the "Paradoxically" that reefs "flourish even though they are surrounded by ocean waters that provide few nutrients."
- (C) True: The passage lists "urban and agricultural runoff and water pollution" as threats, which are forms of water contamination.
- (D) True: The passage says deep and cold water corals exist "on smaller scales," and that reefs are "most commonly found at shallow depths," implying they do not occupy a vast part of the entire ocean surface.
- (E) True: The passage states reefs are "very sensitive to water temperature" and are under threat from "climate change," indicating temperature is crucial for their survival.
Coral reefs are underwater structures made from calcium carbonate sec
[#permalink]
08 Nov 2025, 14:34
08 Nov 2025, 14:34
Expert Reply
Question 2
The passage provides information that helps answer all of the following questions about coral reefs EXCEPT:
(D) What protects coral reefs?
Explanation:
- (A) How are coral reefs formed? Yes: "Corals are colonies of tiny living animals... Most coral reefs are built from stony corals, and are formed by polyps that live together in groups."
- (B) What are the threats to coral reef systems? Yes: Threats are listed as "climate change, ocean acidification, blast fishing, cyanide fishing," etc.
- (C) What are coral reefs called? Yes: "Often called 'rainforests of the sea'..."
- (D) What protects coral reefs? No: The passage describes the protection the coral exoskeleton provides for the polyp ("provides support and protection for the body of each polyp"), and it mentions that the reefs themselves provide "shoreline protection" for land, but it never describes what measures are taken to protect the reefs themselves from the listed threats.
- (E) Where are coral reefs found? Yes: "Most commonly found at shallow depths in tropical waters," with others in deep/cold water.
The passage provides information that helps answer all of the following questions about coral reefs EXCEPT:
(D) What protects coral reefs?
Explanation:
- (A) How are coral reefs formed? Yes: "Corals are colonies of tiny living animals... Most coral reefs are built from stony corals, and are formed by polyps that live together in groups."
- (B) What are the threats to coral reef systems? Yes: Threats are listed as "climate change, ocean acidification, blast fishing, cyanide fishing," etc.
- (C) What are coral reefs called? Yes: "Often called 'rainforests of the sea'..."
- (D) What protects coral reefs? No: The passage describes the protection the coral exoskeleton provides for the polyp ("provides support and protection for the body of each polyp"), and it mentions that the reefs themselves provide "shoreline protection" for land, but it never describes what measures are taken to protect the reefs themselves from the listed threats.
- (E) Where are coral reefs found? Yes: "Most commonly found at shallow depths in tropical waters," with others in deep/cold water.
