Scientists are convinced___the positiveeffect of laughter___physical and mental health.

It was only when the car pulled up in front of our house ___________we saw Lily in the passenger seat.

18．——would you like to go and see the film with me this evening——I am sorry, I can’t because I ________myhomework.

The climbers _____ their ambition by reaching the summit of the mountain.

He didn’t go to the party not ______the time but _____he was ill.