Required to & obliged to are used for...
Obligation & necessity
Name the modal verbs of ability.
Can, could, be able to.
Which modal verb is used to indicate an obligation coming from someone else?
Have to
What are the modal verbs of duty and advice?
Should/shouldn't, ought to/oughtn't to
What is the difference between can and might?
...
What are related verbs used for permission?
Be allowed to/be permitted to
What are the modals of prohibition?
Can't, couldn't, mustn't
There ... be life on other planets. (pissibility)
could/might
At my previous job we ... make personal calls during worktime. (prohibition)
were forbidden/ weren't allowed/ couldn't
She ... cook better than anyone I know! (ability)
can
It was a long and exhausting trip but I ... to enjoy the drive.
managed
You ... worry to much. Take a deep breath, think and make a plan. (no obligation)
needn't
You really... to be an expert to make such a statement. (duty and advice)
ought
I ... leave soon, it's getting late. (obligation and necessity)
must
