一My flight was delayed because of________ heavy rain.—But you are just in______________ time for the discussion.
The old man stood there with his eyes ______ on the picture.
Scientists are convinced ______ the positive effect of laughter ______ physical and mental health.
---I’m going out tonight. ---Well, I’d rather you ______.
Bitten twice, the postman refused to ______ our letters unless we changed our dog.
______ to go abroad alone is what worries me most.