We must be there before the boss comes.?
It is necessary for us to be there on time.?
Study the following explanation
Must is stronger than have to and indicates urgency or stresses importance.
e.g.: They have to attend the Friday Fresh at 7 sharp.
The leader must be a model. do not have to = lack of necessity
must not = prohibition
e.g.: She doesn’t have to work overtime if
she can finish her work now.
You mustn’t tell anyone what I said.
Obligation adalah merupakan kata benda,dalam bahasa Indonesia bertarti kewajiban
Contoh : Youa are under no obligation ( Anda tak ada kewajiban apa-apa)
do not have to = lack of necessity ; must not = prohibition