16. Everyone do his duty. a) have to b) should c) is to
17. You have broken the device. You have read the instructions carefully.
a) must b) should c) had to d) need to
18. “You’re running high temperature, you drink lots water”, the doctor instructed me.
a) must b) should c) have to d) need to
19. I feel I speak to him today, otherwise it’ll be too late.
a) should b) have to c) must d) am to
20. You tell her that you’re sorry. I could always rely on my mother’s advice.
a) must b) should c) had to d) need to
21. It’s my day off, I go to work today.
a) mustn’t b) needn’t c) shouldn’t d) don’t have to
22. I don’t feel well. I quite understand I see a doctor.
a) should b) have to c) must d) am to

16. The correct answer is b) should. "Everyone should do his duty" means that it is expected or recommended for each person to fulfill their responsibilities.

17. The correct answer is b) should. "You should have read the instructions carefully" implies that it would have been better or advisable for you to read the instructions before breaking the device.

18. The correct answer is b) should. "You should drink lots of water" suggests that it is recommended or advisable for you to drink a significant amount of water due to the high temperature.

19. The correct answer is a) should. "I should speak to him today" indicates that it is advisable or the right thing to do to have a conversation with him today, as otherwise it might be too late.

20. The correct answer is b) should. "You should tell her that you're sorry" implies that it is recommended or the right thing to do to express your apologies to her. The sentence also suggests that I always trusted my mother's advice.

21. The correct answer is c) shouldn't. "I shouldn't go to work today" suggests that it is not recommended or appropriate for me to go to work because it's my day off.

22. The correct answer is a) should. "I should see a doctor" implies that it is recommended or advisable for me to visit a doctor since I don't feel well.

It's important to note that the explanations provided are based on the given options and may not cover all possible alternatives. Additionally, language usage can vary, so context is crucial in determining the most appropriate answer.