PREP07逻辑加强题求解

toogy123

46. (33987-!-item-!-188;#058&007200)
Archaeologists in Michigan have excavated a Native American camp near Dumaw Creek. Radiocarbon dating of animal bones found at the site indicates that the camp dates from some time between 1605 and 1755. However, the camp probably dates to no later than 1630, since no European trade goods were found at the site, and European traders were active in the region from the 1620's onward.
Which of the following, if true, most strengthens the argument?
(A) Due to trade among Native Americans, some European trade goods would have reached the area before the European traders themselves did.
(B) At all camps in the region that have been reliably dated to the late 1620's, remains of European trade goods have been found.
(C) The first European trade goods to reach the area would have been considered especially valuable and preserved as much as possible from loss or destruction.
(D) The first European traders in the area followed soon after the first European explorers.
(E) The site is that of a temporary camp that would have been used seasonally for a few years and then abandoned.

background:在密西根发现了camp,根据同位素测定camp应该是1605---1755年之间的，
因为：在那没发现european goods ,而在那里1620年之后才兴起欧洲trade goods的
结论：camp应该是1630年之前

答案：  B

A CDE都很好判断
B : 所有1620年之后的camp都有european goods.

我的疑问是 B 加强了前提， 但是即使加强前提， 结论为什么是camp是1630年之前存在的？  

多谢啦 ， 总之这道题绕的我有点晕