chọn từ hợp lý trong ngoặc

10. About one-third of the Vietnamese (works, work) in agriculture.

11. The number of employees (is; are) approximately five thousand.

12. Half of the students (doesn't, don't) understand a word he says.

13. A number of students (wants/ want) to go to Boston next month.

14. There (is, are) some interesting pictures in today's paper.

15. A lot of time (is, are) needed to learn a language.