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。