You can't imagine what great difficulty I had 【finding】his address.
“I had”在这里作为difficulty的后置定语,所以括号要考的短语是“have difficulty doing something”。
Tim and John have a lot of hobbies 【in common】,especially in surfing the Internet.
“have something in common”是固定短语,表示“有xxx的共同之处”。
就是选C:finding,imagine后面用动词ing形式!
下一题是选A。