Narration(叙述) 1
Unit 1 1
Unit 2 8
Unit 3 17
Unit 4 25
Unit 5 36
Description(描述) 46
Unit 6 46
Unit 7 55
Unit 8 66
Unit 9 77
Unit 10 88
Exposition(说明) 96
Unit 11 96
Unit 12 104
Unit 13 112
Unit 14 122
Unit 15 132
Argumentation(议论) 142
Unit 16 142
Unit 17 151
Unit 18 162
Unit 19 174
Unit 20 183