The plan _________ just because people were unwilling to cooperate (合作).
— Could I have a word with you, mum? — Oh dear, if you __________.
—Is Jack on duty today? —It __________ be him. It’s his turn tomorrow.
As you worked late yesterday, you __________ have come this morning.
— Must he come to sign this paper himself? — Yes, he __________.
If it were not for the fact that she __________ sing, I would invite her to the party.