so as to的用法

Roro666

我感觉so as to 好像有主动的因素存在。SB DO STH SO AS TO BALALA。。但是下面这题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(A)

E.gradual enough so that one cannot distinguish them
答案却是选A。假如C是 SO GRADUAL THAT THEY ARE indistinguishable 的话，应该怎么选呢？
跪求各位大虾赐教

Roro666

再补充 ：OG10-171. In 1527 King Henry VIII sought to have his marriage to Queen Catherine annulled so as to marry Anne Boleyn.
(A)    so as to marry
(B)    and so could be married to
(C)    to be married to
(D)    so that he could marry
(E)    in order that he would marry
Key: D
这题怎么又会选D呢

jaffa23

第二题的so as to 是以至于的意思，后面缺少主语he也就是king henry ，所以用he 代替。

Roro666

楼上说的。好像跟我问的不大对应- -。。不是很懂

Fadaways

so  as to 用于句子中只有单一主语核心词且很明确的情况下，且to do与前面的so  as不能相距太远。第二题中出现了king和queen两个名词，如果用so as to则不能说明哪个是主语，而第一题核心词很明确，就是shifts，所以可以用so as to。另外楼主说的第一题的另外那个选项，语法上应该是正确的，但是与A比起来，应该A会更简洁。