单选题 In this section, you will hear a monologue. The monologue will be read twice. After the monologue, there will be a one-minute pause. During the pause, read the questions and the four choices marked A, B, C and D, and decide which is the best answer. Then mark the corresponding letter on the answer sheet with a single line through the centre. Questions 16 to 20 are based on the passage you've just heard.
单选题 What evolutionary change in birds led to a nest's building?
  • A. Their flying ability improved greatly.
  • B. They became warm-blooded.
  • C. They began to lay eggs.
  • D. They live in cold places.
【正确答案】 B
【答案解析】[听力原文] Many egg-laying animals merely lay their eggs and leave. Turtles, for instance, and horseshoe crabs, the eggs are hatched and the little ones are on their own. The current theory about birds is the earliest birds did just that when they were cold-blooded creatures living in warm places. However, when they became warm-blooded creatures living in cold places, they had to remain on the eggs to keep them warm. For this, they needed a place—a nest. Very likely, the first nest was just a primitive hole scraped in the ground. Even now many species still lay eggs in this sort of crude nest. Primitive nests found on the ground were fine for some birds, but others began to elevate their nests in branches, perhaps to avoid predators. These early elevated nests were probably cup-shaped nest. This type is still built by some birds today. The latest development in nest, the most recent vision, so to speak, is the cup-shaped nest. This is the one we regard today as the typical bird's nest, you know, like a robin's nest. 文中此句For this, they needed a place—a nest中的For this是指上文when they became warm-blooded creatures living in cold places, they had to remain on the eggs to keep them warm，故B项正确。
单选题 According to the speaker, the first bird's nest was located
  • A. on the ground
  • B. in the cold places
  • C. on the highest branches of trees
  • D. in the caves
【正确答案】 A
【答案解析】文中提到the first nest was just a primitive hole scraped in the ground，故A项正确。
单选题 According to the speaker, what is the possible reason that birds began to build nests in trees?
  • A. To avoid predators.
  • B. To expose the eggs to stronger sunlight.
  • C. To have a better view of predators.
  • D. To avoid the nest blown away by wind.
【正确答案】 A
【答案解析】根据此句others began to elevate their nests in branches, perhaps to avoid predators，可知A项正确。
单选题 What is the latest development in nest?
  • A. A hole scraped in the ground.
  • B. Cup-shaped nest.
  • C. Platforms of sticks and dried leaves.
  • D. A round nest.
【正确答案】 B
【答案解析】从倒数第二句The latest development in nest, the most recent vision, so to speak, is the cup-shaped nest. 可知鸟巢的最新形式是杯状。
单选题 What is the main topic of the talk?
  • A. How birds learn to build nests.
  • B. Why birds lay eggs.
  • C. How bird's nests have evolved.
  • D. Why birds become warm-blooded.
【正确答案】 C
【答案解析】本文主要围绕鸟巢展开叙述，一开始，鸟类lay their eggs and leave；后来随着鸟类进化，需要一个nest。而nest刚开始建在地上，后来建在树上，由此可以看出整篇文章是讲鸟巢的演变，故C项正确。