3) if you are hungry, you have some pizza.
a) mustn't
b) could
c) should
4) you give me some water, please?
a) could
b) must
c) should
5) if you are tired, you go to bed early.
a) should
b) could
c) might
6) pupils to bring textbooks to school.
a) might
b) have
c) should
! ​

3) If you are hungry, you should have some pizza.

c) should

4) Could you give me some water, please?

a) Could

5) If you are tired, you should go to bed early.

a) should

6) Pupils have to bring textbooks to school.

b) have

Объяснение:

3) Если вы голодны, вам следует съесть пиццу.

с) должен (= "следует")

4) Не могли бы вы дать мне немного воды

а) мог бы

5) Если вы устали, вам следует лечь спать пораньше.

а) должен (= "следует")

6) Ученики должны приносить учебники в школу.

b) должен (= "вынужден")