Unit 1 1
Text 1 1
Text 2 8
Text 3 16
Text 4 23
Unit 2 31
Text 1(配有视频) 31
Text 2 38
Text 3(配有视频) 44
Text 4 51
Unit 3 58
Text 1 58
Text 2 64
Text 3 71
Text 4 78
Unit 4 86
Text 1 86
Text 2 93
Text 3 100
Text 4 107
Unit 5 115
Text 1 115
Text 2 122
Text 3 129
Text 4 136
Unit 6 144
Text 1 144
Text 2 151
Text 3(配有视频) 158
Text 4 165
Unit 7 174
Text 1 174
Text 2(配有视频) 181
Text 3 187
Text 4 195
Unit 8 203
Text 1 203
Text 2 209
Text 3 217
Text 4 223
Unit 9 231
Text 1 231
Text 2 238
Text 3 246
Text 4 254
Unit 10 262
Text 1 262
Text 2 268
Text 3 276
Text 4 283