Question

read the passage. rethinking coral reefs coral reefs are one of earths most crucial ecosystems, supporting over seven thousand species of marine animals. however, coral reefs are severely threatened by environmental pressures such as rising global water temperatures, the increasing acidity of the oceans, and pollution. more than half of earths coral reefs have been lost since 1950. the rapid depletion of reef habitats has led marine biologists to use genetics to intervene. using an approach called \assisted evolution,\ a team of researchers from the university of hawaii has studied how to breed corals with mutations that make them better able to withstand changing ocean conditions. if these hardier corals can be placed among wild corals, scientists hope that entire reefs may be able to adapt to and survive environmental pressures as they continue to intensify. what is the main, or central, idea of the passage? scientists are trying to address damage to reefs by breeding corals that are able to survive in warmer and more acidic oceans. \assisted evolution\ studies the kinds of genetic mutations that make organisms less susceptible to changing environmental conditions. the preservation of coral reefs is important because thousands of marine species depend on the reef ecosystem for survival.

Explanation:

The passage first emphasizes the importance of coral reefs and the threats they face. Then it focuses on scientists from the University of Hawaii using "assisted evolution" to breed corals that can better withstand environmental changes. The main idea should capture this effort to address reef damage. The first option does this as it combines the threat (warmer and more acidic oceans) and the solution (breeding resilient corals). The second option is too narrow, only focusing on the concept of "assisted evolution" without the context of reef - damage. The third option only highlights the importance of reefs, not the efforts to save them.

Answer:

Scientists are trying to address damage to reefs by breeding corals that are able to survive in warmer and more acidic oceans.