题目

阅读理解 Despite their bad reputation, sharks are critical to the marine ecosystem and can even help fight climate change. In the shallows of Shark Bay, Western Australia, seagrass is food for the sea cows, which can weigh as much as 500 kg and eat roughly 40 kg of seagrass a day. Sea cows are a rich source of food for tiger sharks. By keeping the sea cow population in check, tiger sharks help seagrass meadows（草地） thrive. A flourishing seagrass meadow stores twice as much CO₂per square mile as forests typically do on land. But tiger shark numbers are declining. Off Australia's northeast coast of Queensland, tiger sharks are estimated to have fallen by at least 71 percent, largely due to overfishing. A reduction in tiger sharks means more seagrass consumed by herbivores（食草动物） and less carbon stored in sea vegetation. This begged the question: What if they were absent from the Shark Bay—would the seagrass-dominated ecosystem survive? To find out, researchers led by Rob Nowicki of Florida International University, spent time in Eastern Australia, where shark numbers were lower and sea cows ate seagrass largely undisturbed. "When uncontrolled, sea cows can rapidly destroy wide areas of seagrass, "said Nowicki. " When the seagrass recovers, the seagrass community looks different, with more tropical species dominating than before. " Those findings underlined the role that tiger sharks were playing in Shark Bay. If their populations continue to decline, the resilience（恢复能力） of carbon-rich ocean ecosystems will likely decrease. When it comes to boosting shark numbers, there have been movements toward more sustainable fishing, but a large percentage of the industry have not changed their methods, which is a reason why the population of many marine top predators（捕食者） continues to decline. Apart from supporting sustainable fishing, Nowicki said the only way to truly protect marine life is to reduce our global greenhouse gas emissions. "Ultimately, if we are going to conserve our ecosystems in the centuries to come, we are going to need to solve climate change while undertaking species conservation at the same time." （1） Why are tiger sharks key to the marine ecosystem? A . They feed on various sea animals. B . They can store large amounts of CO₂. C . They can prevent the loss of seagrass. D . They affect marine species distribution. （2） What did Rob Nowicki's team want to find out in Eastern Australia? A . How sea cows destroy the seagrass community. B . How shark population influences the ocean ecosystem. C . What was contributing to the declining number of tiger sharks. D . What to do to recover the seagrass-dominated ecosystem. （3） What is the main reason for the decline in tiger shark numbers in Australia? A . Climate change. B . Seagrass Loss. C . Habitat destruction. D . Unsustainable fishing. （4） What is important in preserving marine life and ecosystems suggested by Nowicki? A . Banning marine fishing activities. B . Addressing ocean pollution problems. C . Preserving marine top predators. D . Decreasing greenhouse gas release. 答案： C B D D

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