Unit 1 Genetic Story 1
Unit 2 Transportation 11
Unit 3 Custom 20
Unit 4 Business in America 29
Unit 5 Language Study 38
Unit 6 Ecology 48
Unit 7 Internet 58
Unit 8 Love and Marriage 68
Unit 9 Society 78
Unit 10 Technology 88
Unit 11 Technology Makes Life Convenient 97
Unit 12 Travel and the Environment 108
Unit 13 Famous Cities in the World 119
Unit 14 Celebrities 129
Unit 15 Entertainment 140
Keys 151