I still don't know who ___while I was away from home .A happened _英语解答

I still don't know who ___while I was away from home .
A happened B had happened (为什么不能选择b）

人气：466 ℃　时间：2020-01-26 05:34:09

解答

那个好像不是who 应该是what吧
while 动词时态并列所以选A