33.You can't imagine what difficulty we had ______ home in the snowstorm.[2007 辽宁卷]A.walked B.walk C.to walk D.walking为什么选D?

you can't imagine walking home is very hard.
动名词

have difficulty (in) doing

Have difficulty doing sth,difficulty被提前了

固定搭配
have difficulty in doing sth.
其中的in可以省略~

have difficulty doing sth
what difficulty we had 是个从句

D. walking
应该是what difficulty we had (in doing sth)
考察 have difficulty in doing sth