Mrs Green went to the shop to buy some salt, _ the baby _ after by her.第一空是left还是leaving

题目

Mrs Green went to the shop to buy some salt, _ the baby _ after by her.第一空是left还是leaving
主语是Mrs Green,那不是应该选leaving吗?答案为left.
请高手求助

答案

不要太迷信答案,答案又不总是对的
我觉得是leaving.
第一个空应该填非谓语动词,Mrs Green 是主语,和baby的关系是主动的,因此用leaving