39. Most archaeologists have held that people first reached the Americas less than 20,000 years ago by crossing a land bridge into LACE w:st="on">North AmericaLACE>. But recent discoveries of human shelters in South America dating from 32,000 years ago have led researchers to speculate that people arrived in LACE w:st="on">South AmericaLACE> first, after voyaging across the Pacific, and then spread northward.
Which of the following, if it were discovered, would be pertinent evidence against the speculation above?
A. A rock shelter near LACE w:st="on">Pittsburgh, PennsylvaniaLACE>, contains evidence of use by human beings 19,000 years ago.
B. Some North American sites of human habitation predate any sites found in LACE w:st="on">South AmericaLACE>.
C. The climate is warmer at the 32,000-year-old South American site than at the oldest known North American site.
D. The site in LACE w:st="on">South AmericaLACE> that was occupied 32,000 years ago was continuously occupied until 6,000 years ago. B
E. The last Ice Age, between 11,500 and 20,000 years ago, considerably lowered worldwide sea levels.
做完题目,再仔细一想, B中说发现北美的居民比南美的还早...的确削弱了原文的结论.
那么是不是也同时削弱了原文的提干, 比南美还早的话, 就不可能是20000年前到达的拉,应该还要早啊....
这样把原文中的提干也一起削弱也可以么? | 
