people didn't know what_____(happen）during the night

people didn't know what_____(happen）during the night
people didn't know what_____(happen）during the night

people didn't know what_____(happen）during the night
根据句子里的didn't 可以得知这是已经发生的事了,所以用happen的过去式happened,这句话也是考察what happened的用法,这个短语多数是用在对方问另一方发生什么事的时候用

happened 填过去时 didn't

填will happen,表示将来时态