请教：一道真题

The soft drink company’s flat earnings reflect the extent to which poor currency exchange rates are keeping down profits for multinational companies.

A.      reflect the extent to which poor currency exchange rates are keeping

B.      reflect the extent of poor currency exchange rates keeping

给出的答案是B,但是我怎么看都觉得应该选A呀。

tianwan兄的解答是正确的，偶的帖子就不放在这里丢人了。A is definitely preferable than B.

偶一开始在A中看到了一个好像intrusive 的时态，are keeping，感觉没有indicator.

现在想然，其实to which这个介词短语可以做状语来employ进行时态，而且B中分词的逻辑主语的确有致命错误。

1,I think B may be not so good.

B is actually " the extent of poor rates keeping down profits".  The center word after "extent of" is "keeping down".  

I personally take it that "extent of" normally precedes noun, not gerund.

2, I can't see anything wrong in A.  I think A is actually" poor rates keep profits down to such an extent".

Maybe my idea is not correct. But, according to my current knowledge and experience, in real test I will choose A.

Sorry, I can't explain it more clearly. NN's ideas are appreciated.