单选题 For Question 11～20, you will hear two passages. Before listening to each one, read the questions related to it. While listening, answer each question by choosing A, B, C or D. You will hear each piece ONLY ONCE.
单选题 Which is not a new finding of this research?
  • A. Old formula for calculating species extinction is erroneous.
  • B. Extinction possibilities were greatly overestimated.
  • C. There is no threat to the survival of species.
  • D. Species extinct at a less rapid rate.
【正确答案】 C
【答案解析】[听力原文] A team of scientists claim that a widely-used formula for calculating whether certain plant or animal species is becoming extinct is deeply flawed, and might overestimate extinction possibilities by as much as 160 percent. The researchers say that while their finding suggests a less rapid rate of global extinctions, serious threats remain to the survival of many plant and animal species. Back in the early 1980s, environmental biologists predicted that as many as half of the world's species of plants and animals would be lost by the year 2000. That did not turn out to be the case, according to the research team. They say a new analysis of a mathematical formula widely used to calculate extinction rates shows the world's plants and animals may have a little more time. To determine whether a species is headed for extinction, scientists conventionally count the number of plants and animals encountered in areas of different sizes to come up with the species-area relationship. Then, they extrapolate backwards to predict how many species will be lost as their habitats shrink due to human encroachment and other forms of habitat destruction. Stephen Hubbell, a tropical forest ecologist at the University of California, said there's a problem with this counting strategy. Becuause it makes the assumption that if you lose the first individual you encounter, that species is committed to extinction, and clearly that isn't true. Hubbell said that to calculate extinction more accurately, scientists need to keep increasing the land area they sample rather than decreasing it. According to their mathematical formula, Hubbell said the problem of species extinctions is not as dire as is widely believed.
单选题 Which statement is true about the prediction in the early 1980s?
  • A. More than half of the world's species would extinct by the year 2000.
  • B. Less than half of the world's species would extinct by the year 2000.
  • C. The prediction has been proved to be true.
  • D. The prediction turned out to be not true.
【正确答案】 D
【答案解析】
单选题 What is the conventional measurement based on?
  • A. Species-area relationship.
  • B. Human encroachment.
  • C. Forms of habitat destruction.
  • D. The change of habitats.
【正确答案】 A
【答案解析】
单选题 According to Hubbell, to calculate extinction more accurately, scientists need to ______.
  • A. increase the sample land area
  • B. decrease the sample land area
  • C. varify the sample land area
  • D. keep the sample land area unchanged
【正确答案】 A
【答案解析】
单选题 What is the main topic of this passage?
  • A. A new problem of environmental protection.
  • B. The invention of a mathematical formula.
  • C. The counting strategy of species extinction.
  • D. Species extinction rates are greatly overestimated.
【正确答案】 D
【答案解析】