Grammar Part-3. USAGE OF - "Should ,Must, Have, Mustn't and don't have"

USAGE OF - "Should ,Must,Have, Mustn't and don't have"

Mustn't - not allowed

don't have - not necessary

Should - when sth is best, correct, best.
Have - Necessary or compulsary.

Must - when one is sure that sth is true.

                                                                    Examples :-