考博英語模擬試題及答案

考博英語模擬試題
Part I Listening Comprehension(15 points) (略)
Part II Reading Comprehension (40 % )
Directions: There are 4 reading passages in this part. Each passage is followed by some questions or unfinished statements. For each or them there are four choices marked A, B, C and D. You should decide on the best choice and then mark the corresponding letter on the Answer Sheet.
Questions 16 to 20 are based on the following passage:
Eight times within the past million years, something in the Earth's climatic equation has changed, allowing snow in the mountains and the northern latitudes to accumulate from one season to the next instead of melting away. Each time, the enormous ice sheets resulting from this continual buildup lasted tens of thousands of years until the end of each particular glacial cycle brought a warmer climate. Scientists speculated that these glacial cycles were ultimately driven by astronomical factor: slow, cyclic changes in the eccentricity of the Earth's orbit and in the tilt and orientation of its spin axis. But up until around 30 years ago, the lack of an independent record of ice-age timing made the hypothesis untreatable.