请教BY白勇语法第四章33题（p101）

According to United States Air Forces 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 has proved itself helpful to demonstrate

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

追加一问：

根据白勇的语法复习，如下是分词和that从句做定语的区别

【ed/ing/定语从句做定语】

1.     
                        ed  强调某一次，结果，无重复

2.      ing 强调多次性，重复性，客观性，无明确时间概念

3.      定语从句
                    强调一次性，强调具体时间，具体行为

其中，ed和that的部分不是很清晰。

如果问题中增加

F. shot dead chickens at airplanes has proved helpful in demonstrating

那么怎么区别E和F呢？

不是"不停的把鸡射到飞机上的加农能证明"，而是"一次射一只鸡到飞机上的加农能有力地证明blah,blah..."

helpful如果后面要跟to do，前面是要用形式主语it来引导句子的.

helpful的搭配基本上有两种：helpful in doing, helpful to sb./sth.

不能这么改.

过去分词不能引导非限定性分句（shot dead chickens at airplanes这个表达是不对的）.

能说的在具体点么？

谢谢啊。

umm...换个说法就是，shot放在名词a cannon后面有两个可能用法：1、被动语态做形容词，表示cannon被执行shoot这个动作，显然应该是cannon执行shoot这个动作，而不是被执行。2、过去时态，这里明显不是。

所以不能用shot。

I have found the original sentence from nytimes.

"Officials at Langley Air Force Base said today that a cannon that hurls dead chickens at airplanes at 700 miles an hour is helping to reduce accidents caused by jets hitting birds. "