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.

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?