61. D prepating → to prepare
62. B thorough interested → thoroughly interested
63. A addressed and stamped → Afer addressing and stamping
64. A possible → possibly
65. B quietly → quiet
66. C mathematic
67. B three-speeds → three-speed
68. B much
69. C as
70. C bỏ much
71. B get
72. D not to talk
73. A were
74. D come
75. A has seen
76. D went
77. B can the world
78. C hadn't to
79. A thinking
80. A bỏ not