hrough the customs at the capitalairport, I had to pay _____ on the camera I had bought.

____ all of you are top students, only one will be chosen for the coming competition.

The poor boy couldn’t work the problem out. He wasn’t ____clever.

If we cannot __________ the subject of astronomy，we won’t get the job opportunities on space stations.[ ]

Shall I help you?—Sure. Such a difficult case is ______ I could handle myself.