StephenHawking believes that the earth is unlikely to be the only planet _lifehas developed gradually.

You should try to get a good night sleep____ much work you have to do.

Do you walk to school every day—I used to walk, but now I ride to school _______ walking.

If better use is ____ of your spare time, you’ll make great, progress in it．[ ]

You don’t know ______ I want to see you again. It’s ayear since I last saw you.