doing...是不是不能做主语？(大全55为例)

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

答案E

由此例想到，是不是GMAT里动名词不能做主语？