— I can’t give up smoking, doctor.For your health, I’m afraid you _______.
My parents like the music ____ is quiet and gentle.
We often see Betty ____ the old man with his housework.
In our city, _____ middle school students want to work as a teacher in the future.
I found _____ necessary to save energy and protect the environment.
________ beautiful these postcards are! Where did you get them?