—Can we go camping tomorrow，as planned?—I'm afraid not.The dark clouds ________a heavy rain.

In much of the animal world，night is the time________for sleep—pure and simple.

 Finding information in today's world is easy.The ________ is how you can tell if the information you get is useful or not.

You’d better    smoking, or you will get ill.

You can easily _______ this question if you study British history.