求问逻辑题

Candycatgmat

对这题中时间有点弄不清楚，求思路，多谢了！

Charcoal from a hearth site in Colorado, 2,000miles south of Alaska, is known to be 11,200 years old. Researchers reasoned that, since glaciers prevented human migration south from the Alaska - Siberia land bridge between 18,000 and 11,000 years ago, humans must have come to the Americans more than 18,000 years ago.

Which of the following pieces of new evidence would cast doubt on the conclusion drawn above?

A. Using new radiocarbon dating techniques, it was determined that the charcoal from the Colorado site was at least 11,400 years old.

B. Another campsite was found in New Mexico with remains dated at 16,000 years old.

C. A computer simulation of glacial activity showed that it would already have been impossible for humans to travel south overland from Alaska 18,500 years ago.

D. Using new radiocarbon dating techniques, it was proved that an ice-free corridor allowed passage south from the Alaska- Siberia land bridge at least 11,400 years ago

E. Studies of various other hunting - gathering populations showed convincingly that, once the glaciers allowed passage, humans could have migrated from Alaska to Colorado in about 20 years.

caixinni

题目说 在C发现的木炭可以追溯到11200年前。 但是研究者说冰河使得人类在18000年前到11000年前 这段时期中不能迁往 Alaska - Siberia land bridge 以南，所以他们说人类在18000以前就已经在美洲了。

因此我们需要找到一个答案提供一种方式或证据 使得人类在18000年前到11000年前 这个区间内到达美洲。

答案应该是D。

Candycatgmat

书上的答案是D。我不明白的是at least 11,400 years ago 好像不能削弱， ice-free corridor 完全有可能在18，000年或再之前， 因为11，400之前嘛

xxllin

题目是说东东是11200年代的，但是由于18000到11000年都不能通行，所以这段时间不可能有。

D选项说了从11400年前就可以通行了，所以该东东可以有。因为11200年在11400年以后了，所以通行以后可以有了。