[求助]新prep 174

174.      (28920-!-item-!-188;#058&003515)

Often major economic shifts are so gradual as to be indistinguishable at first from ordinary fluctuations in the financial markets.

A. so gradual as to be indistinguishable

B. so gradual so that they can be indistinguishable

C. so gradual that they are unable to be distinguished

D. gradual enough not to be distinguishable

E. gradual enough so that one cannot distinguish them

答案是A

但是我觉得C也可以的吧。。。

so ...as to 和so...that到底怎么区别啊。。。bow

我认为有2个原因:

1.indistinguishable和be unable to be distinguished在语言色彩上有不同;

2.主动优于被动;

在网上查了一下,发现so...as to和so that的用法没什么区别.