What is this passage mainly about? The use of coral in the construction industry

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions

Coral polyps can truly be called the animals that helped make the world. For uncounted generations, trillions upon trillions of coral polyps have built structures called reefs, larger in scale than those of any other living beings, including humans. The stone-like material created by these tiny animals becomes limestone, a prized building material that was used to construct the Great Pyramids of Egypt. Huge deposits of limestone exist underground, beneath the ocean, in islands, and in mountains. Limestone has been used in the construction of countless churches, castles, train stations, and banks, and crushed limestone is a major ingredient of cement.

Living coral reefs are remarkable “cities beneath the sea,” filled with a rich variety of life. These undersea ecosystems thrive in the warm, shallow oceans near the equator. Among the world’s most colorful places, coral reefs are full of brilliantly colored fish and coral covered in wonderful patterns. Reef fish are an important food source for humans and make up a significant percentage of the global fish catch.

In recent years, various factors have threatened coral reefs and the life that depends on them as their home. Blast fishing is an illegal fishing method which involves setting off bombs in the water to kill as many fish as possible. Its negative effects on a reef are significant; it kills most living things and causes great damage to the reef’s structure. Fishing with liquid cyanide, a very dangerous and deadly material, is another threat to reef ecosystems, particularly in the Philippines. Fishermen release liquid cyanide into the reef and collect the stunned fish, which are then sold for big money to the aquarium market, or for consumption in restaurants. The fishermen often break apart the reef to look for hiding fish. The cyanide also kills large numbers of coral polyps, leaving large areas of the reef dead.

Reefs are also damaged when coral is taken for building material, jewelry, or aquarium ornaments. Water pollution also results in damage. In addition, the recent warming of the oceans has caused areas of many reefs to turn white. Biologists are concerned that coral may be negatively impacted by further warming.

Threats to coral reefs are serious, but there is reason to hope that they will manage to survive. If we take steps toward coral reef conservation, it is likely that these tiny creatures, which have survived natural threats for millions of years, will be able to rebuild the damaged reefs that so many ocean animals and plants depend on.

(Adapted from Reading Explorer 2 by Paul Maclntyre)

What is this passage mainly about?

• A. The use of coral in the construction industry
• B. The wonder of coral reefs, and their threats
• C. The kinds of fish found near coral reefs
• D. The underwater world in general