The classroom is so dirty that it needs________ badly.
The scientist knew nothing about the matter, because he was always _________ himself in his study.
He said he _________ his work, and then we needed to wait for him for a little while.
How pleasant the picture is to _________!
Jack went to college last year, _________ to return home until he achieves his goal.
— What’s that terrible noise? — The boys _________ for a party.