prep 1-174 so as to 的用法。。。

dpp0405

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

C怎么不对呢？究竟什么时候用so as to 啥时候用 so...that...呢？关键so as to be 貌似和so as to do 还有啥区别的，望高手解惑！不胜感激！

bycsscsq

c中unable不能用被动～～

星。燃

同问，还有一道……so that he can marry Anna 和so as to marry Anna 的题，都在prep2008上, 求指点~

jiaoguitar

刷OG可以看到，GMAC很少直接告诉你是so...that好，还是so as to好，还是in order to好。在OG之外，很多网友对此进行的总结，我觉得有参考意义，但是只要不是OG说的就不能够作为绝对的标准。如何区分这些词组，我个人觉得主要还是看句意，以及他们和其它词组的搭配。

这个题首先排除D和E，原因不多说了。然后排除B因为搭配错了，so...that是正确搭配，so...so that错。C有两个错误，一个绝对错误，就是出现了able/unable to be done的结构，这个OG上有写是绝对错的；另一个错误是相对错误，就是出现了they这个代词。They可能引起各样的指代歧义，比如本句中可能指shifts，也可能指后面的markets。