_____ teens are using the Internet for both social and intellectual development, they are also facing significant challenges on how to manage their relationships online.

I always had doubts he would be the best man for the job , but now I don’t doubt he can do it.

Please don’t say a bad word about anyone.一________.

Mum, would you please buy me an ipad— If you can help do the dishes the whole vacation, you ______ have one as a reward.

下列各句中，没有语病的一项是（ ）