I heard a man_at that time.But I didn't know who he was.

问题描述:

I heard a man_at that time.But I didn't know who he was.
A.spoke B.speaks C.to speak D.speaking

同意楼上的答案D,关键还在于后面那个时间是at that time指的是就在那个时间,应该是正在进行的.