We often use (1)_____ to ask for and give permission. We also use (2)_____ to ask for permission (but not to give it). (3)_____ is more formal and polite than (4)_____. (5)_____is the most formal way to ask for and give permission. - We use (6)_____ and (7)_____ to show that something is prohibited it is not allowed. We use(8)_____ to talk about something that is against the rules, particularly when we didn't make the rules. We use (9)_____ to talk about what is not permitted. It is common on public signs and notices informing people of rules and laws. We use (10)_____ and (11)_____ express obligation. There is a slight difference between the way we use them. (12)_____ shows us that the obligation comes from outside the speaker, we sometimes call this 'external obligation'. (13)_____ expresses a strong obligation or necessity. It often shows us that the obligation comes from the speaker (or the authority that wrote the sentence). We use (14)_____ and (15)_____ to show that there is no obligation. You can do something if you want to but it's not compulsory.​