Tom took the police to the spot ____ the accident happened．

Polly said that he did everything ______ she could to comfort his sister who cried after being refused by Harvard.

If you try to sit on two chairs,you will fall them .For life,you must choose one chair.[ ]

Be sure _______ when you enter the cave. Otherwise, you’ll hit your head on the rocks.

Do you often play basketball _____ your friends? [ ]