He was busy writing a story , only once in a while to smoke a cigarette.
A. to stop
B. stopping
C. to have stopped
D. having stopped
网友回答
A. to stop
(答案→)B. stopping
C. to have stopped
D. having stopped
解析：考察分词作状语。现在分词表示意料之中的结构，不定式表示意料之外的结果。句意：他忙于写故事，只是偶尔的停下来抽支烟。故B正确。他太忙，所以偶尔停下来是正常的事情。