If he fails again, he will __________ us all __________ with him.
The two girls are so alike that strangers find ______ difficult to tell them apart.
He is busy now, otherwise he ______ go with you for a walk.
Having a trip abroad is certainly good for the old couple, but it remains _____ whether they will enjoy it.
---How long will you stay here? ---I don’t know. ________.
Since then the number of people taking driving lessons _______ 20%.