Unit 1 The Developing World 1
Topic 1 Our country has developed rapidly 1
Topic 2 What a large population! 19
Topic 3 Project Hope has changed my life 27
Unit 2 Loving Our Planet 39
Topic 1 Pollution causes too many problems 39
Topic 2 All these problems are very serious 52
Topic 3 Would you like to be a greener person? 66
Unit 3 English around the World 78
Topic 1 English is widely used throughout the world 78
Topic 2 English is spoken differently in differ-ent countries 92
Topic 3 Could you give us some advice on how to learn English well? 103
Unit 4 Surprising Science 114
Topic 1 The spaceship is mainly controlled by computers 114
Topic 2 When was it developed? 126
Topic 3 We will live in space one day 136
词汇表（按字母顺序排列） 150
不规则动词表 169