托福阅读真题及答案（3）

托福阅读真题及答案（3）

paragraph3— 4

We do not know.Ecologist Paul S.Martin has championed the model that associates the extinction of large mammals at the end of the Pleistocene with human predation.With researcher J.E.Mosimann,he has co-authored a work in which a computer model showed that in around 300 years,given the right conditions,a small influx of hunters into eastern Beringia 12,000 years ago could have spread across North America in a wave and wiped out game animals to feed their burgeoning population.

The researchers ran the model several ways,always beginning with a population of 100 humans in Edmonton,in Alberta,Canada,at 11,500 years ago.Assuming different initial North American big-game-animal populations(75–150 million animals)and different population growth rates for the human settlers(0.65%–3.5%),and varying kill rates,Mosimann and Martin derived figures of between 279 and 1,157 years from initial contact to big-game extinction.

6.Which of the sentences below best expresses the essential information in the highlighted sentence in the passage?Incorrect choices change the meaning in important ways or leave out essential information.

A.A computer model was designed to determine how long it would have taken for a small group of hunters to spread across North America.

B.A computer model showed that it was possible for a small group of hunters to spread across North America and kill off game animals in just 300 years.

C.According to a computer model,people coming into North America 12,000 years ago had to kill game animals in order to feed their population.

D.According to a computer model,about 12,000 years ago conditions enabled a small group of hunters to enter and cross North America in about 300 years.

正确答案：B

7.Which of the following best describes the results of the research discussed in paragraph 4?

A.Scientists used mathematical models to show that most of the extinctions occurred in areas where humans had recently arrived.

B.Scientists established that the main population of North Americans who hunted lived in Canada during the time of the megafauna extinctions.

C.Scientists used numerical models to confirm that a small population of humans could have caused big-game extinctions in a relatively short period of time.

D.Scientists used statistics to prove beyond doubt the currently accepted view that human hunters were the main cause of the megafauna extinctions.

Paragraph 4 is marked with an arrow

正确答案：C