71. I will leave the party early because I must studying for my exam. A B C D 72. I stayed up late last night because I mustn't go to school on Sunday. A B C D 73. We ought to not play football as it's raining outside. A B C D 74. You mustn't to drive a car if you don't have a driving licence. A B C D 75. If you want some useful advice, you have better talk to your parents about your problem. A B C D 76. I had stay at home 3 days due to snowing heavily. A B C D 77. Because of his poverty, he has to struggling to make ends meet. A B C D 78. According to the rules of this game, you had better not drop the ball. A B C D 79. If you want to get a higher mark in the next test, you have better put more effort into vocabulary. A B C D 80. We shouldn't make an appointment with this doctor. You can see him whenever you want. A B C D