【简答题】A More than two thirds of the world ’ s polar bears will be wiped out by 2050 , according to a shocking new study.By then , scientists say , global warming will have melted 42 percent of the Arctic se...
【单选题】听力原文: During the nineteenth century, when little was known about environmentalism and conservation, it was common to hear people say that the resources of the sea were unlimited. They believed the wor...