. — What’re you going to do to protect the environment? — Plant trees on side of the river.

I think trees ____________ twice a week in such hot weather.—Yes, I agree. Or they may die without water.

Only when the work is done ________ be able to go back home.

If it_______ rain tomorrow, I’ll go climbing with my classmates.

It was the first time ________ I ________ face to face with a thunder storm.