Parents cannot take care of them ________, so children should learn to be independent.

─Why did you pull the girl─You see，traffic was so busy that anything happen to her at that moment.

The findings support another study which showed that being happy ______ reduce the risk of heart disease.

下列各句中，没有语病的一句是（ ）

Many clothing manufacturers now substitute artificial silk _____ natural silk to cut down costs of production