Must and need are modal auxiliary verbs. Must expresses ideas as such as strong obligation, compulsion etc. Need expresses ideas such as necessity. Must not shows prohibition. Need not shows lack of obligation or necessity.
Fill in the blanks with must not or need not.
1You ............... invite Sabu. I don't want him to come.
Wrong!
Must not shows prohibition.
2You ............... invite her. She won't come.
Wrong!
3You ............... tell anybody about my decision. It is a secret.
Wrong!
4You ............... make a noise. The baby is sleeping.
Wrong!
Must not shows prohibition. Need not shows lack of necessity.
5You ............... reserve a table. It is not very busy in the morning.
Wrong!
6You ............... quit this job before you find another one.
Wrong!
7You ............... waste your time on idle pursuits.
Wrong!
8Those who have already registered ............... register again.
Wrong!
9You ............... rush. You can take your time.
Wrong!
10You ............... have told her. She already knew about it.
Wrong!
11You ............... waste food.
Wrong!
12You ............... have cooked so much food. Nobody was hungry.
Wrong!
Done.
Score: 0/12
Answers
- You must not invite Sabu. I don’t want him to come.
- You need not invite her. She won’t come.
- You must not tell anybody about my decision. It is a secret.
- You must not make a noise. The baby is sleeping.
- You need not reserve a table. It is not very busy in the morning.
- You must not quit this job before you find another one.
- You must not waste your time on idle pursuits.
- Those who have already registered need not register again.
- You need not rush. You can take your time.
- You need not have told her. She already knew about it.
- You must not waste food.
- You need not have cooked so much food. Nobody was hungry.

