He was busy writing a story,only ____...

问题描述:

He was busy writing a story,only ____...
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
为什么不选A 为什么是伴随状语?

B、stopping
现在分词做伴随状语,补充说明was busy的
问题补充:答案选B 为什么不选A
不定式表将来,动名词表伴随