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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