51. A (avoid + V ing)
52. a (need + V ing: cần được làm gì)
53. b (advise sb to do sth)
54. a (need + V inf)
55. a (had better + V inf)
56. d (try to do sth/ delay doing sth)
57. b
58. d (regret + v ing: hối hận vì đã làm gì)
59. c (for + v ing)
60. a (detest doing sth)
61. a (can + v inf)
62. b (decide to do sth)
63. c (enjoy + v ing)
64. d (be able to do sth)
65. b (try to do sth)
67. b (agree to do sth)
68. a
69. c
70. c
71. b
72. c
73. d
74. a
75. d
76. c
77. d
78. b
79. b
80. c
81. a
82. b
83. b
84. d
85. d
86. a
87. b
