51. All students ____ wear uniforms at school because it is a rule. A. should B. have to C. ought to D. must 52. You ____ finish your homework before you go to bed. A. must B. have to C. should D. ought to 53. This drink isn't beneficial for health. You ____ drink it too much. A. should B. ought to not C. ought not to D. mustn't 54. This warning sign indicates that you ____ step on the grass. A. shouldn't B. mustn't C. don't have to D. ought not to 55. I think you ____ do exercise regularly in order to keep your body in good shape. A. must B. should C. ought to D. Both B and C 56. I will lend you some money, but you ____ pay it back to me next week. A. should B. have to C. must D. mustn't 57. Hoa ____ feed the cats because her mother has done it already. A. has to B. doesn't have to C. must D. Both A and C 58. Those audiences ____ show their tickets before entering the concert hall. A. have to B. must C. ought to D. don't have to 59. The children ____ spend too much time playing computer games. A. mustn't B. ought to not C . shouldn't D. Both B and C 60. In case you're suffered from the injury, you ____ see the doctor today. A. had better B. must C. ought D. have better