大全 section 3-23

[wawa0916]

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) that shoots dead chickens at airplanes has proved helpful in demonstrating
答案是E 為什麼會用in????

[hsudk]

helpful + in 是idiom，要背起來。

help 才是加不定式(to，可省略)

[r123581]

那請問 prove + adj + in + Ving 也是idiom嗎？
搞不太清楚中..

[hsudk]

prove 的標準用法之一：

[linking verb]if someone or something proves difficult, helpful, a problem etc, they are difficult, helpful, a problem etc:

The recent revelations may prove embarrassing to the President.