which floor does your friend _____ the building?a.live in b.live in on c.live in in d.live on
问题描述：
which floor does your friend _____ the building?a.live in b.live in on c.live in in d.live on
答
应该是live on inwhy把句子还原一下就清楚了：My friend lives on the third floor in this buiding.