unit 1 ................................................................................................................................................................ 1
unit 2 ................................................................................................................................................................ 9
unit 3 .............................................................................................................................................................. 16
unit 4 .............................................................................................................................................................. 23
unit 5 .............................................................................................................................................................. 31
unit 6 .............................................................................................................................................................. 40
unit 7 .............................................................................................................................................................. 47
unit 8 .............................................................................................................................................................. 54
unit 9 .............................................................................................................................................................. 62
unit 10 ............................................................................................................................................................ 71
unit 11 ............................................................................................................................................................ 80
unit 12 ............................................................................................................................................................ 88
unit 13 ............................................................................................................................................................ 96
unit 14 ......................................................................................................................................................... 104
unit 15 ......................................................................................................................................................... 111
unit 16 ......................................................................................................................................................... 119
unit 17 ......................................................................................................................................................... 127
unit 18 ......................................................................................................................................................... 134
unit 19 ......................................................................................................................................................... 141
unit 20 ......................................................................................................................................................... 148
unit 21 ......................................................................................................................................................... 155
unit 22 ......................................................................................................................................................... 162
unit 23 ......................................................................................................................................................... 170
unit 24 ......................................................................................................................................................... 178
unit 25 ......................................................................................................................................................... 185
unit 26 ......................................................................................................................................................... 193
unit 27 ......................................................................................................................................................... 201
unit 28 ......................................................................................................................................................... 208
unit 29 ......................................................................................................................................................... 215
unit 30 ......................................................................................................................................................... 224
以下为对购买帮助不大的评价