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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

what is different "shooting" and "that shoots"

分词和定语从句修饰时：

分词表示连续性反复动作

定语从句表示一次性行为