He was so busy his homework that he forgot to have supper.A. to doB. doC. doingD. does

问题补充：

He was so busy his homework that he forgot to have supper.

A. to do

B. do

C. doing

D. does

答案：

A. to do

B. do

(答案→)C. doing

D. does

解析：句意：他总是忙着做功课，以至于忘记吃晚饭。be busy doing sth忙于做某事，固定句型，故选C