Sure, here are the best answers circled:

11. They meet their friends and ... some fun.
A. take B. have C. do D. enjoy

12. You should pay more ... in class.
A. part B. care C. notice D. attention

13. He and his friends usually get ... and talk about their stamps.
A. together B. themselves C. each other D. one another

14. He likes stamps. He is a stamp ...
A. collect B. collecting C. collector D. collects

15. Some students say they are ... They have no time for pastime.
A. hurry B. busy C. full D. hard

16. It's difficult to cross this street because there is too much ...
A. crowd B. traffic C. people D. transport

17. There aren't any good movies ... at the moment.
A. going on B. being on C. performing D. showing

18. Sorry I can't come but thanks ...
A. any ways B. any way C. anyway D. in anyway

19. Look at ... girl over there.
A. one B. this C. that D. a

20. Would you like to come to my house for lunch?
A. Yes, I do B. I'd love to C. Yes, I like D. OK. I'd like