so difficult ____it to live in an English-speaking country that i determined to learn English

问题描述:

so difficult ____it to live in an English-speaking country that i determined to learn English
A.i have felt B.have i felt
C.i did feel
d.did i feel
选哪个.为什么?

D
这是个倒装句.
例如:
So fast did he run that we can't catch up with him.
这句话又是过去时,所以选D.