托福阅读真题及答案（6）

托福阅读真题及答案（6）

Though Martin claims the lack of evidence actually supports his model—the evidence is sparse because the spread of humans and the extinction of animals occurred so quickly—this argument seems weak.And how could we ever disprove it.As archaeologist Donald Grayson points out,in other cases where extinction resulted from the quick spread of human hunters—for example,the extinction of the moa,the large flightless bird of New Zealand—archaeological evidence in the form of remains is abundant.Grayson has also shown that the evidence is not so clear that all or even most of the large herbivores in late Pleistocene America became extinct after the appearance of Clovis.Of the 35 extinct genera,only 8 can be confidently assigned an extinction date of between 12,000 and 10,000 years ago.Many of the older genera,Grayson argues,may have succumbed before 12,000 B.C.,at least half a century before the Clovis showed up in the American West.

[■]Although the climate changed at the end of the Pleistocene,warming trends had happened before.[■]A period of massive extinction of large mammals like that seen about 11,000 years ago had not occurred during the previous 400,000 years,despite these changes.[■]The only apparently significant difference in the Americas 11,000 years ago was the presence of human hunters of these large mammals.[■]Was this coincidence or cause-and-effect?

12.Paragraph 7 suggests that Donald Grayson believes which of the following about the remains at Clovis sites and megafaunal extinctions?

A.The rapid rate of the spread of humans explains why the extinctions also occurred at a rapid rate.

B.The lack of evidence of human-caused extinctions is not surprising in view of the speed with which the extinctions occurred.

C.It is likely that more evidence will be found as dating methods improve.

D.If humans did contribute to the extinctions,much more evidence of that would have been found by now.

Paragraph 7 is marked with an arrow

正确答案：D

13.Look at the four squares[■]that indicate where the following sentence could be added to the passage.

One possible nonhuman cause—weather cycles—is not consistent with what scientists know about the timing of the extinctions.

Where would the sentence best fit?Click on a square[■]to add the sentence to the passage.

正确答案：A