(1) Coral reefs are underwater habitats made from limestone secreted by coral. (2) These rich ecosystems are formed when coral p
olyps, which are tiny animals living in colonies, die and leave behind a branched, stony material. (3) The reefs made from this material provide a home to many animals including sponges, sharks, eels, jellyfish, anemones, sea stars, shrimp, and turtles. (4) Some of these animals are on endangered lists, and marine biologists are struggling to help them thrive.
(5) Unfortunately, many coral reefs are dying. (6) Threats to the reefs include water pollution from sewage and agricultural waste, dredging of the ocean floor near the coast, or collecting of coral in a careless manner. (7) In addition, man-made projects can deprive coral reefs of light, which they need to survive. (8) Projects related to mining or construction can cloud the waters which blocks the light and kills coral. (9) Finally, global warming has damaged a lot of reefs in the world. (10) Even a one-degree change can cause the degradation of a reef.
What does the author use to support the central idea in the second paragraph?
A. personal experiences that illustrate the endangered status of the reefs
B. examples of activities and phenomena that are harmful to coral reefs
C. interviews with marine biologists about the future of coral reefs
