Prep 1 - 46请ＮＮ指教因果关系，不懂，搜了也不懂

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.

不知道有没有欧洲货和判断ＣＡＭＰ年代之间有什么关系！还有不明白1620和1630是否是搞错了，还是有玄机呀．　

我选的Ｃ，因为觉得没有办法，可能是说如果有欧洲货来了，ＣＡＭＰ里就应该有吧，既然没有被保存，就是之前的ＣＡＭＰ．　但是欧洲货是1620年来的呀，为什么结论说ＣＡＭＰ不晚于1630年？

答案是Ｂ，我不懂，即使说其他1620的遗址有欧洲货，怎么能够证明没有欧洲货的遗址就是不晚于1630年.

ＣＤ上的解释都很含糊，而且解答中明显把欧洲货1620来又说成了1630. 所以我觉得问题没有解决呀！贵请高人指教！本人9月4日就要考了．

问题类型：加强

逻辑过程：

前提：欧洲贸易商从1620‘s（1621~1629）开始在该地区从事贸易活动；然而没有在camp考古现场发现有贸易物品。
结论：camp的历史时期要早于1630年。（就算欧洲贸易商最晚从1629年开始从事贸易活动，那么从1930开始该地区就应该有贸易物品了。）

我是这样理解的：无贸易物品发现 ---> camp的历史时期与欧洲贸易商的历史时期无交集。

选项B说：在所有处于历史时期1620‘s（1621~1629）的camp中都发现有贸易物品。
            （camp的历史时期与欧洲贸易商的历史时期有交集 --->有贸易物品发现）所以加强（只是支持，不是证明）

我是照着lawyer_1的方法【选项是否在某方面帮助了作者】想的，大家看看有无问题。

终于明白了，我的问题在于对1620's没有理解透彻！太谢谢了