Underline the correct modal verbs:1) Scientists don't have to/must consider the dangers of cloning.2) People mustn't/don't have to be experts to operate a DVD player.3) You must/mustn't switch off your computer when it is not i...

Underline the correct modal verbs: 1) Scientists don't have to/must consider the dangers of cloning. 2) People mustn't/don't have to be experts to operate a DVD player. 3) You must/mustn't switch off your computer when it is not in use. 4) She has to/mustn't be 20 years old now. 5) You have to/mustn't be careful with electricity. 6) People don't have to/mustn't take computer lessons to use a computer. 7) John mustn't/has to study hard if he wants to become a robotics engineer.