gwd 41逻辑 谢谢

dpzixuan89

charcoal from a hearth site in Colorado, 2000miles south of Alaska, is known to be 11200 years old. Researchers reasoned that, since glaciers prevented human migration south from the Alaska-Siberia land bridge between 18000 and 11000 years old, humans must have come to the Americas more than 18000 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 Colarado site was at least 11400 years old.

B another campsite was found in New Mexico with remains dated at 16000 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 18500 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 11400 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 Colarado in about 20 years.

不太明白题目什么意思，，答案选D

bdsjb116

原文说since glaciers prevented human migration south from the Alaska-Siberia land bridge between 18000 and 11000 years old，说明它认为人不可能在这段时间从c到a

D说有个有个corridor是可以让他们穿越的，因此削弱了结论。