I make an appointment with Dr. Smith this afternoon— Sorry, I’m afraid he is not ______ because he has a patient to operate on.

I_____the problem _____in my mind for a whole week before I did anything about it.

When he looked up，he suddenlyfound himself ______by a group of teenagers，____looked athim anxiously.

_______ laws of motion are simple, motion, as we see it in the world about us, certainly is not

I still can’t believe my eyes when I remember the scene________the best player should miss the pass