1.Who knocked at the door so loudly?I don’t know.

问题描述:

1.Who knocked at the door so loudly?I don’t know.
I don’ t know ____ _______ at the door so loudly.
2.Do you know ______ else is going to be on duty today?(who,whom)
3.I really don't know________ the bridge will be finished.(how long,how soon)

1 who knocked
2 who
 做从句的主语,所以用who
3 how soon
后面有will,表示将来时,用how soon,问多久
我不知道这桥多久就能修好