mustn't / don't have to

This exercise is based on the language presented on page 113 of How English Works

Match the items on the right with the items on the left.

It is forbidden. You ______ do that.
You ______ ask my permission. You can do what you want.
You ______ speak to the driver when the bus is moving. It's dangerous.
Help yourself to anything you want. You ______ ask.
You ______ park here. There is a double yellow line.
Pay me back when you can. You ______ do it immediately.
It's optional. We ______ to go if you don't want to.
I'll tell you a secret. You ______ tell anybody else. Promise?
Whatever you do, you ______ click with the right mouse button or the program will crash.
Be on time. You ______ be late or we will leave without you.
He's a millionaire. He ______ work but he does because he enjoys it.
I like Saturdays because I ______ go to work.
This is very important. You ______ forget what I said.
It's very infomal here. You ______ wear a tie unless you want to.
The train is direct. You ______ change trains.
In boxing, you ______ hit your opponent below the belt.
I ______ wear a suit at work on Fridays. It's 'dressing down day".
In athletics, you ______ start before the gun is fired.
In bridge, you ______ look at other people's cards.
You ______ be mad to work here but it helps.

Your score is