Choose the correct answer

17. Study harder ___ the exam.

A. if you will fail

B. and you would fail

C. unless you fail

D. or you will fail

18. The girl wishes she ___ in Hue for the festival next week.

A. had stayed

B. was staying

C. stay

D. could stay

19. Miss Lan stopped ___ her letter because she had to leave for the hospital.

A. to write

B. write

C. writting

D. wrote

20. Do you know the man ___ car Jack is driving?

A. who

B. whom

C. which

D. whose