求助：逻辑大全TEST1-20

PhoebeOMG

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




想不明白，求解释求解释！！！

alzn2765

因果推理找削弱：

前提（因）：在中层底部发现了大毁灭之后用的瓶瓶罐罐，但是底层没有发现类似的东西。
结论（果）：考古学家应该在中层和底层寻找被毁灭的城市的遗迹（中层底部都是大毁灭之后用的瓶瓶罐罐，那么一定在底层了呗）

因--->果
这个推理可以成立需要建立在一个Assumption上：每层里面的东西的位置不能变，永远留在那一层形成的时候的位置。

A就是否定了这个前提：使得因 无法推出 果 自然削弱的目的就达到了。
A的意思是有一种挖洞的动物G，会挖一个大洞，有时候洞塌了，里面的东西会跟着塌了的洞一起往下掉。

如果有地震，会产生断层，把上一层的东西震到下一层去，这个选项也是正确的。

PhoebeOMG

alzn2765 发表于 2015-9-12 11:30
因果推理找削弱：

前提（因）：在中层底部发现了大毁灭之后用的瓶瓶罐罐，但是底层没有发现类似的东西。

哦哦哦！！原来是这样子！！谢谢alzn2765