6. (Q) Choose the correct answer. In 1950, people phones. use mobile A) should't B) should C) can't D) couldn't 7. (Q) Choose the correct answer. When longer. his mother was young, she skate but she can't do it any A) couldn't B) could C) should D) can' 8. (Q) Choose the correct answer. We from the inside! open the door: it was locked A) could B) should C) couldn't D) mustn't 9. (Q) Choose the correct answer. It's cold. You A) couldn't B) could C) should D) shouldn't 10. (Q) Choose the correct answer. She's always tired. She every night. go to bed late A) couldn't B) can C) should D) shouldn't wear a cardigan.