--- Look at the black clouds. It ______ soon.　--- Sure. If only we ______ out.

Rain is pouring down from the sky without any sign of stopping．Farmers begin to worry about their crops since it _____ as long as 24 hours．

For some time the expert __________ people of the health risks caused by passive smoking. He     says he won't stop until all the smokers around him decide to quit smoking.

—I’m sorry, but the manager isn’t here yet. Shall I have him call you when he comes back?—No, I’ll call him later. If I call again in half an hour, do you think he       ?

By the 1920s, Howard Carter ____ an explorer.