Question

【题目】He was busy writing the exam paper, only ___once in a while to check the time.

A. to stop B. stopping

C. to have stopped D. having stopped

Answer 1

【答案】B

【解析】考查分词做状语。He与stop构成主动关系，使用现在分词的形式。句意：他忙于做试卷，只是偶尔停下来核对一下时间。