He is sweating heavily. He _______ weightlifting for a long time.

I went to see my friends off at the airport.—Is that_____you were late for the important meeting?

hat do you think of genetically modified food (转基因食品) —We all think ______ is careless ______ somescientists to say it is safe before doing any experiment.

You should feel content, as the design can’t be done any ______.

Two men were ____ to death on the mountain because it was _____.