Certainly I posted your letter---I remember it.A. postingB. to postC. to be postingD. have

问题补充：

Certainly I posted your letter---I remember it.

A. posting

B. to post

C. to be posting

D. have posted

答案：

(答案→)A. posting

B. to post

C. to be posting

D. have posted

解析：remember doing sth.意为“记得曾经做过某事”，remember to do sth.意为“记住要做某事。”