HW due 29th of Feb. 2012

Permission, Prohibition, Obligation, No obligation

To express permission, prohibition, obligation and no obligation we usually use modal verbs.

Permission

Can is often used to ask for and give permission.

• Can I sit here?
• You can use my car if you like.
• Can I make a suggestion?

We can also use may and could to ask for and give permission but can is used more
often.

Prohibition

Can’t  is used to show that something is prohibited – it is not allowed.

• You can’t park here, sir.
• You can wear jeans but you can’t wear trainers in that bar.
• You  can't speak when the teacher is speaking.

Can’t tells us that something is against the rules. 

Obligation

Have to is used to express obligation.

Have to shows us that the obligation comes from somebody else. It’s a law or a rule and the speaker can’t change it.

• Do you have to wear a uniform at your school?
• John can’t come because he has to work tomorrow.
• In Britain you have to buy a TV licence every year.

No obligation

We use don’t have to to show that there is no obligation. You can do something if you want to but it’s not compulsory.

• You don’t have to wear a tie in our office. You can wear a tie if you want to but it’s OK if you don’t.
• It’ll be nice if you do but you don’t have to come with me if you don’t want to.
• You don’t have to dress up for the party. Wear whatever you feel comfortable in.

Instructions: Complete the following sentences with can / can't / have to / don't have to.

1.- Olinca students ______________ wear uniform on Mondays.

2.- The students ____________ use moblie phones in class.

3.- 5th graders _______________ call their teachers "Sir" or "Miss", they can use their names.

4.- 5th B _____________ get another pizza party if they speak in English all the time!