大全-3-23

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

(A) shooting dead chickens at airplanes has proved helpful to demonstrate

(B) shooting dead chickens at airplanes has proved itself helpful as a demonstration of

(C) shooting dead chickens at airplanes proves itself helpful as demonstrating

(D) that shoots dead chickens at airplanes proves itself helpful to demonstrate（E）

(E) that shoots dead chickens at airplanes has proved helpful in demonstrating

答案: E

A 为什么不对?   一定要用定语从句吗?

－ing修饰，表示持续的动作

that修饰，表示明确的单词动作，BY或者是LZM说的

但我觉得现在不适用了，做GWD和prep的时候，没见过一定要用这种判断做题的