v-ing形式的用法

题目

v-ing形式的用法
-Henry doesn't seem like the same person.
-（ ）so much in the war has made him more thoughtful.
1,For him to see 2, His seeing 3,Having seen 4,To be seeing
我认为应该选3,但答案选择的是2,不懂啊.求解.

答案

选3.你已经知道这是在考ing用法,动词ing形式这里做状语.因为是已经看到的经历才让他更懂得怎么思考,所以用完成时态的ing形式.