C. Underline the best answer.
16. Which one of the pair expresses an obligation?

A. I must go to the dentist

B. I will go to the dentist.


17. Which one of the pair expresses necessity?
A. You have to be very careful in choosing friends.

B. You can be very careful in choosing friends


18. Which one of the pair expresses moral obligation?

a. Parents should teach their children how to make good decision.

a. Parents must teach their children how to make good decision.


19. Which one of the pair expresses more formal and polite way of saying that someone has permission?

a. Students may travel free.

b. Students can travel free.


20. Which one of the pair expresses polite way of asking permission to do something?

a. Could we go home now?
b. Can we go home now?​