补充

littlebluesk

83 At the time of the Mexican Agrarian revolution, the most radical faction, that of Zapata and his followers, proposed a return to communal ownership of (land, to what had been a pre-Columbian form of ownership respected by the Spaniards.)

正确答案是a，但是我不太了解 to what 这种结构。谁给讲讲？

85 According to United States Air Force officials, a cannon (shooting dead chickens at airplanes has proved helpful to demostrate) what kind of damage can result when jets fly into a flock of large birds.

d:that shoots dead chickens at airplanes proves itself helpful to demonstrate
e:that shoots dead chickens at airplanes has proved helpful indemonstrating

我选的d,答案选e,  不懂为什么用完成时。

linsonstudy

根据语境可以判断用完成时较佳,具体我也讲不清楚。
而此题也可从prove入手，prove的用法有
(1) prove (to be) adj./sth. in sth. 后面接的是名词，
如： 1)The little boy has proved his cleverness in the television quiz.
       2)a theory that proved impractical in practice.
(2)prove sth. to sb.
如：can you prove it to me?
(3)......
但是一般不用as。。。 和 to   
不好意思，有事要出去，没有详讲。88