题目

    In spring 2008, the polar bear was placed on the endangered species list. According to the Endangered Species Act, an endangered species is an animal that is likely to face extinction in its natural habitat. Polar bears have been categorized as a" threatened" species.   66 .The polar bear is the first animal that has been classified as endangered due primarily to global warming. Global warming is caused by carbon dioxide and other greenhouse gases that become trapped in the atmosphere. Heating homes, driving cars, and burning garbage all require fossil fuels that lead to global warming.     The polar bear's habitat is more vulnerable(易受影响的)to global warming than many other species. Polar bears live mainly on the sea ice in the Arctic. This is where they hunt for fish and build up fat reserves.  67 .In the Arctic, global warming is causing the ice to melt slightly earlier and form slightly later. This results in a shorter feeding season for the polar bear. Some risk their lives to find ice. If they have to swim too far they will drown from exhaustion and hunger. The World Wildlife Fund estimates that nearly 25% of the Arctic sea ice has disappeared in the past 30 years.     It is not the polar bear that is at risk in Arctic. Every species of plant, animal, and insect there is threatened by global warming. Nevertheless, environmentalist groups such as the World Wildlife Fund often study large carnivores(食肉动物)in order to assess the health of an ecosystem.  68  . In addition, donations are more commonly offered for the protection of large animals such as bears or elephants. People in general are less interested in conversation efforts that protect small wildlife such as plants or insects.     69  . Once they are on the list there are laws that protect these animals from being hunted for food or sport. Agencies also receive money and tools to protect the habitat and recover the species. The goal of removing the animal from the list is often achievable. Since the Endangered Species Act was introduced in the U.S. in 1973, many species have been taken off the list due to increased populations..        A. It is not rare for a species to go extinct after they make the list.        B. The Arctic food chain relies on the polar bear.        C.A threatened species is one that is likely to become "endangered" in the foreseeable future.        D. It is important that animals such as polar bear make it onto the endangered species list.        E. When the ice melts, many polar bears move to land and live off their stored fat.        答案： CEBD 

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