UnitⅠ：Sea and Land Animals 1
Chapter 1 Sharks: Useful Hunters of the Sea 2
Chapter 2 A Brief History of Horses with Humans 10
UnitⅡ：Language and Culture 21
Chapter 3 Learning a Second Language 22
Chapter 4 Food and Culture 32
UnitⅢ：Exercise and Fitness 43
Chapter 5 The Importance of Exercise for Children 44
Chapter 6 The New York City Marathon: A World Race 54
UnitⅣ：Remarkable Researchers 65
Chapter 7 Margaret Mead: The World Was Her Home 66
Chapter 8 Louis Pasteur: A Modern - Day Scientist 76
UnitⅤ：Science and History 85
Chapter 9 The Origin of the Moon 86
Chapter 10 Maps: The Keys to Our World 96
UnitⅥ：Future Technology Today 107
Chapter 11 Saving Lives With Weather Forecasting 108
Chapter 12 Clues and Criminal Investigation 120
Index of Key Words 132
Answer Key 140