me he walked up to me smiling.A. To seeB. For seeingC. On seeingD. Because seeing

问题补充：

me, he walked up to me, smiling.

A. To see

B. For seeing

C. On seeing

D. Because seeing

答案：

A. To see

B. For seeing

(答案→)C. On seeing

D. Because seeing

解析：考查介词词组;on /upon doing sth“一做…”，句意是：一看见我，他就微笑着朝我走来。选C。