Each teacher and each student ... to try their best to finish their work

Chọn đáp án đúng:
1.Each teacher and each student_______to try their best to finish their work
A. have
B. having
C. to have
D. has
2.What__________ in the living room at this time last Monday?
A. happened
B. had happened
C. has happened
D. was happening
3. No one has to leave for the country, ___________?
A. has he
B. have they
C. does he
D. do they
4. There_________ changes of the climate for the last ten years.
A. are
B. has been
C. have been
D. were