用所给词的正确形式填空。
1.I think there _____(be) fewer trees next year.
2.He _____ (collect) 300 pictures since 5 years ago.
3.Sam always _____(help) his classmates.
4.Would you mind _____ (play)the games after school?
5.My father came into the bedroom while I ____ (dance)
6.American fast food seems_______ (be) the most popular in the world.
7.My mother made me ______(clean) my room all by myself yesterday.
【答案】
1. will be 解析：句末明显的时间标志，next year，应该用一般将来时，will+动词原形。
2. has collected 解析：这是现在完成时很经典的句子，由since引导时间状语或是时间状语从句。更常考的是，since加过去时的句子，主句用现在完成时的情况，比如说：He has lived China for 4 years sice he moved here in 2005.
3. helps 解析：本题有标志词always，用一般现在是，要注意主语是第三人称单数，动词要用单三形式。
4. playing 解析：would you mind +doing sth，动词的这类用法需要不断积累和归纳。
5. was dancing 解析：本题中的状语从句由while引导，强调的是同时性，应该用进行时，由于主句中用了过去时态，后文应对应的使用过去进行时。
6. to be 解析：固定用法，seem to，好像—后面直接跟动词原形。
7. clean 解析：本题考查使役动词make的用法，make sb do sth。更有难度一点的题应该是考查使役动词的被动态，应该是be made to do sth.