请教逻辑

春天的花儿会开

是补充材料上面P163，19,20两题共用一篇文章，刚刚入门，请教一些逻辑的基本问题，谢谢！
Archaeologists seeking the location of a legendary siege and destruction of a city are excavating in everal 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.
Which of the following hypothesses 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 confused 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.
the key:C
记着大牛mindfree曾经说要active reading.这篇文章应该没有结论对吧？文章两句话都是evidence吧？而题让我们找出这个结论。但是如果C要是个结论的话好像还少点什么？不知道该怎么想。
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 scollapse.
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 foreces 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. Bothe the middle and the lower layer show evidence of large-scale destrction of habitations by fire.
e. Bronze axheads of a type used at the time of the siege were found in the lower lever of excavation.
the key :A
不知道为什么，似乎扯得远了点。
多谢各位斑竹的帮忙。本人水平实在是很菜，刚刚考完T打算考G。

mindfree

I think these questions must have been expained before.

I would say that it is pretty straight-forward.

The chronology is siege --> destruction --> pottery of type 3.

So if the pottery is found in the layer, the layer should represent a era later than the siege.

BTW, A in question 1 is not correct as it cannot be supported by the evidnece. For example, the upper layer in my backyard might contain some artifact later than the destruction. I cannot hypothize that the layer underneath the upper one will represent the siege.

Hypothesis is like a conclusion. A is only "possible", but cannot be concluded.

As to the second question, A simply stated that the pottery does not belong to this layer. So the existence of it does not matter at all. For example: if you find a digital camera being used by native jugle hunter in the amazon rainforest, you cannot conclude that their "tribal" technology is highly developed if you find out that the camera was brought there by a tourist.

春天的花儿会开

谢谢mindfree总教头！

mindfree

Who gave me that title "GMAT总教头"? I did not put it there...

crusaders

好酷啊....