Parents always tell children to stay away from the fire.A. keep on B. keep out C. keep off
—It’s smoggy these days. That’s terrible! —Yes, I hope to plant trees. ______ trees, ______air pollution.
School students ________ smoke because it is against the school rules.
_____ great fun it is to make a snowman in winter.
The flight to London wasbecause of the heavy snow.
Tom is weak in physics. He always feels _______ before he takes a physics test.