题目内容
【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
【答案】B
【解析】句意：他忙于做试卷，只是偶尔停下来核对一下时间。He与stop构成主动关系，使用现在分词的形式，故选B。
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题目内容
【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
【答案】B
【解析】句意：他忙于做试卷，只是偶尔停下来核对一下时间。He与stop构成主动关系，使用现在分词的形式，故选B。