6.
1. B: Perhaps you should leave home earlier.
2. B: Maybe you should talk to her.
3. B: You shouldn't worry so much. It's not helpful.
4. B: Yes,I know. We shouldn't stay much longer.
7.
1. Yes,they should,because school is children's job, and if adults get paid for going to their jobs, children should aswell.
2. Yes, because the Internet is the future, and it being free would help society evolve faster.
3. Yes,because technology is needed nowadays,not only for information,but also for playing games or socialising.
9.
2- a. You don't have to help her.
3- c. You mustn't tell anyone.
4- d. She doesn't have to take medicine any longer.
5- b. I mustn't forget to call him.
