Contents 1
Unit Sixteen 1
Unit Seventeen 32
Unit Eighteen 67
Unit Nineteen 95
Unit Twenty 126
REVISION（Ⅲ） 149
Unit Twenty-One 156
Unit Twenty-Two 180
Unit Twenty-Three 209
Unit Twenty-Four 234
Unit Twenty-Five 264
Unit Thirty 288
REVISION（Ⅳ） 289
Unit Twenty-Six 294
Unit Twenty-Seven 320
Unit Twenty-Eight 339
Unit Twenty-Nine 363
Unit Thirty-One 415
REVISION（Ⅴ） 431
APPENDIX Ⅰ 437
APPENDIX Ⅱ 443
Vocabulary List 451