[求助]大全55

1.        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

正确选项中that修饰cannon，简化过后就是a cannon  has proved helpful in demonstrating，逻辑上不对啊？这题到底应该怎么解释啊？

在某方面，用In.