【题目】You can't imagine what difficulty I had______my oral English when I was a freshman.
A.to improve
B.improved
C.improving
D.improve

【答案】C
【解析】考查固定短语。have difficulty (in) doing sth. 做某事有困难。句意：你难以想象我在大一时，提高英语口语方面遇到什么样的困难。用（in）动词ing形式作状语，此处省略介词in。故选C。