Passage 3 How Clothes Are Made 42
Unit Thirty-five The Man's Invention 45
Passage 1 The Invention of Wheels 45
Passage 2 Making of Paper and Pencil 47
Passage 3 The Invention of Bicycles 49
Passage 4 How Did Stamps Come into Use 51
Unit Thirty-six The Animal World（Ⅰ） 53
Passage 1 Animal Mimics 53
Passage 2 The Frog That Changes Colour 56
Passage 3 Different Groups of Animals 58
Passage 4 The Animal Without a Head 60
Unit Thirty-seven The Animal world（Ⅱ） 62
Passage 1 Insects 62
Passage 2 Ants 65
Passage 3 Fishes 67
Passage 4 Reptiles 69
Unit Thirty-eight The Animal World（Ⅲ） 71
Passage 1 Birds 71
Passage 2 Mammals 74
Passage 3 The Biggest and the Gentlest 76
Passage 4 The World of Microbes 79
Unit Thirty-nine The Balance of Nature 82
Passage 1 The Balance of Nature 82
Passage 2 The Squirrel and The Acorn 85
Passage 3 The Food Chain 87
Passage 4 Our Best Friends-Trees 90
Unit Forty Plants（Ⅰ） 92
Passage 1 Plants 92
Passage 2 Different Types of Leaves 94
Passage 3 Different Types of Stems 96
Unit Forty-one Stories of Nature 98
Passage 1 The Story of Raindrop 98
Passage 2 Water,Steam and Ice 100
Passage 3 The Birth of a Volcano 102
Passage 4 Terrible Earthquakes 105
Unit Forty-two Light 108
Passage 1 Light 108
Passage 2 How Light Travels 111
Passage 3 Reflection of Light 113
Passage 4 Shadows 115
Unit Forty-three Heat 118
Passage 1 What Gives Heat? 118
Passage 2 Heat Travels by Conduction 121
Passage 3 Heat Travels by Convection 123
Passage 4 Shadows 125
Unit Forty-four Sounds 128
Passage 1 Are Sounds Useful or Harmful 128
Passage 2 How Do We Make Sounds? 131
Passage 3 How Does Sound Travel? 133
Passage 4 Sound Has Speed 135
Unit Forty-five Atoms and Molecules 138
Passage 1 Leaning about Molecules 138
Passage 2 Molecules Pull 140
Passage 3 Structure of the Atom 142
Passage 4 Nuclear Energy 145
Unit Forty-six Exploring the Space 147
Passage 1 The Sun and the Stars 147
Passage 2 Air and the Space 149
Passage 3 The First Men on the Moon 151
Unit Forty-seven Social Facts 153
Passage 1 Bells on Your Ears 153
Passage 2 The Rain Dance? 155
Passage 3 Can You Vote? 157
Passage 4 Rich Countries and Poor Countries 159
Unit Forty-eight Schools and Education 161
Passage 1 Why Do Children Go to School? 161
Passage 2 Early American Schools 164
Passage 3 The School onWheels 167
Passage 4 Book in Chains 169
Unit Forty-nine Trade 171
Passage 1 Let's Trade 171
Passage 2 Stone Money,Feather Money 173
Passage 3 Walking,Talking Ads 175
Passage 4 Different Kinds of Money 177
Unit Fifty Communication 180
Passage 1 Forms of Communication 180
Passage 2 Radio 183
Passage 3 Send a Message 186
Unit Fifty-one Festivals 188
Passage 1 Christmas Day 188
Passage 2 Spring Festival 191
Passage 3 April 1st 193
Passage 4 New Year's Eve 195
Unit Fifty-two Signs 198
Passage 1 Signs in the Desert 198
Passage 2 Something for Nothing 200
Passage 3 Sign Language 201
Unit Fifty-three Primitive Methods of Counting 204
Passage 1 A Stone for Sheep 204
Passage 2 A Dusty Way to Count 206
Passage 3 The Rope Stretchers 208
Passage 4 The Year That the Barn Burned Down 210
Unit fifty-four Modern Technology 212
Passage 1 The Machine That Knows the Answers 212
Passage 2 The Structure of a Computer 214
Passage 3 Telephone 216
译文 219
词汇 282
Unit One About Myself 1
Passage 1 My Family 1
Passage 2 My Room 3
Passage 3 My Foreign Friends 5
Passage 4 Our House 7
Unit Two Our School 9
Passage 1 Our Classroom 9
Passage 2 Our School Garden 11
Passage 3 Our English Teacher 13
Passage 4 Our Library 15
Unit Three Learning English 17
Passage 1 The English Language 17
Passage 2 Two Languages Or One 20
Passage 3 How to Use a Dictionary 22
Unit Four The United States 24
Passage 1 The Early Days of the United States 24
Passage 2 Schools in the U.S 27
Passage 3 The Climates of the United States 30
Passage 4 The Capital of the United States 32
Unit Five The United Kindom 36
Passage 1 The Weather in England 36