求助。

vcsanity

Unlike a hurricane, which can be observed from within, a tordado is so small that such a study has not been practical.

B) that studying it that way has not been impractical
C) for such studies as this to have been impractical
D) as to not make such a study practical.
E) as to be impractical of study


为什么不是E呢？
多谢各位！

andreasyang

答案是B吗？
有so的话后面一定要有that啊
感觉GMAT里面，so as to的没一个对的

vcsanity

答案是A。