Help me (正确形式填空)

Help me (正确形式填空)
1.Swimming and bike riding (be)both both good activities during summer months.
2.some people think that banning things (be)useless.
3.The questions raised at the meeting (be)very important.
4.Too little brushing (cause)tooth decay.
5.One of the teenagers (have)this to say about the experience.
6.Three well-balanced meals each day (include)milk,meat,fresh vegetables,and fresh fruit.
7.There (be)a lot of violence in that city.
8.Plenty of exercise (make)us look and feel better.
9.Articles for daily use (be)in abundant supply.
10.What's troubling me (be)that I don't have much experience in this kind of work.
麻烦请写请答题时加上为什么,
填空部分是扩号全面一个地方。
麻烦请在答题时加上为什么，