Please excuse me your letter by mistake. A. to openB. to have openedC. for openingD. in

问题补充：

Please excuse me your letter by mistake.

A. to open

B. to have opened

C. for opening

D. in opening

答案：

A. to open

B. to have opened

(答案→)C. for opening

D. in opening

解析：excuse sb for doing sth 意为“原谅某人做了某事”。