Question

【题目】He was so busy ____ his homework that he forgot to have supper.

A. to do B. do C. doing

Answer 1

【答案】C

【解析】句意：他如此忙着做他的家庭作业以至于他忘记了吃晚饭。to do 是动词不定式形式；do动词原形；doing是动名词形式。这句话中使用的句型是be busy doing sth.忙于做某事，故应选C。