问一道补充材料里面的逻辑：）

Questions 19-20 are based on the following
Archaeologists seeking the location of a legendary siege and destruction of a city are excavating in several possible places, including a middle and a lower layer of a large mound. The bottom of the middle layer contains some pieces of pottery of type 3, known to be from a later period than the time of the destruction of the city, but the lower layer does not.

19. Which of the following hypotheses is best supported by the evidence above?
(A) The lower layer contains the remains of the city where the siege took place.
(B) The legend confuses stories from two different historical periods.
(C) The middle layer does not represent the period of the siege.
(D) The siege lasted for a long time before the city was destroyed.
(E) The pottery of type 3 was imported to the city by traders.

20. The force of the evidence cited above is most seriously weakened if which of the following is true?
(A) Gerbils, small animals long native to the area, dig large burrows into which objects can fall when the burrows collapse.
(B) Pottery of types 1 and 2, found in the lower level, was used in the cities from which, according to the legend, the besieging forces came.
(C) Several pieces of stone from a lower-layer wall have been found incorporated into the remains of a building in the middle layer.
(D) Both the middle and the lower layer show evidence of large-scale destruction of habitations by fire.
(E) Bronze axheads of a type used at the time of the siege were found in the lower level of excavation.

答案分别是c和a。第一题的e选项为什么不可以呢？还有哪位nn能给俺讲讲其中的逻辑关系啊？

这道题是讲：为了研究一个历史事件究竟在哪发生，考古挖掘了几个地点，其中包括一个废墟。考古学家挖掘了这个废墟的中层和下层（有一个预备知识必须知道：越往下年代越久远），在中层的底部（也就是中层和下层之间），发现了些陶罐，这些陶罐标志着比所研究的事件还晚的时间。

题目问能从题干推出什么，只能推出中层不代表事件发生的时间，你说的E选项，讲trader，归纳类型的题，正确答案一定是严格从给你的题干里推出来的，含有新出现的词汇的选项不是答案。

噢噢！！我明白了 使我对题目的理解有问题。谢谢phil

ａ　给出一个他因　。　很简单