Question

The table below provides you with a list of modals that are used to express necessity and permission.

Necessity/obligation	Permission
Positive must    obeying have to    authority need to    right thing ought to    to do should	Positive can (less formal) may (more formal)
Negative must not cannot ought not to	Negative need not do not have to

Answer 1

Necessity/Obligation	Permission
Positive	Positive
must – obeying authority	can – less formal
have to – obligation	may – more formal
need to – necessity
ought to – right thing to do
should – right thing to do
Negative	Negative
must not	need not
cannot	do not have to
ought not to