How do we use the modal verb "must" in these contexts?

[amna]

pl explain me the use of must,

IT must have rained.

She is speaking well, she must practice it.

U must not drop it.

U must do it

pl help me

AMNA

[Torsten]

[amna]

Thanks,

please explain what is the difference between [b]Have to [/b]do and [b]Must do[/b], which should be used in conversation & writing

Thanks again

Amna

[Torsten]

Must is very strong and often means you have no alternative.
_________________
Test Of English for International Communication
TOEIC Preparation & TOEIC Vocabulary