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.

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.（A）

(E) Bronze ax heads of a type used at the time of the siege were found in the lower level of excavation.

答案选a ,我想选c，a 中途应该只能是从上层掉下来呀，所以只能是把pottery的可能出现时间推迟，不是提前阿

说说我的理解

题目问The force of the evidence cited above is most seriously weakened ，就是说evidence 被weaken。你只要找到一个论据说明这个evidence并不能说明挖掘的layer能够代表这个legendery毁灭的时间就可以了削弱evidence的force了

你说“把pottery的可能出现时间推迟，不是提前阿” ，换句话说，不管推迟还是提前都会影响evidence的有效性

题目是说：挖掘的遗址中，中层土壤中找到一些在城市毁灭之后的瓶瓶罐罐,而上层表土本来应该包含这些东东，却没有。（时间越早的，应该埋在越下面，越近发生的，应该埋在越上面，所以evidence提出了一个paradox）。

有点类似于要你找一个explanation。A是最好的答案。

希望对你有帮助。