1 A Arctic and Alpine Tundra 1
1 B A Wilderness Encounter 3
2 A What Is Quicksand? 5
2 B Surviving Quicksand 7
3 A How We Hear 9
3 B Getting a Hearing Aid 11
4 A The Classification of Living Things 13
4 B Plants That Eat Insects 15
5 A How Sunlight Affects Health 17
5 B Cave Life 19
6 A Every Drop Counts 21
6 B Effects of the World' s Water Situation 23
7 A The Endless Struggle Between Predators and Their Prey 25
7 B Attack — and Counterattack! 27
8 A Simple and Complex Carbohydrates 29
8 B Sensible Dieting 31
9 A Heat Energy at Home 33
9 B A Hot Air Balloon 35
10 A The Life Cycle of a Frog 37
10 B It's a Frog! No, It's a Toad! 39
11 A Symbiosis 41
11 B An Alga, a Fungus, and Two Brothers 43
12 A Estuaries and Their Habitats 45
12 B A Protected Beach 47
13 A Snow Travel in the Arctic 49
13 B Learning to Snowshoe 51
14 A What Is the World Wide Web? 53
14 B The Inventor of the World Wide Web 55
15 A A Hall of Gems and Minerals 57
15 B Mining for Diamonds 59
16 A Microbes and Germs 61
16 B Growing Bread Mold 63
17 A The Many Faces of Primatologists 65
17 B Among the Gorillas 67
18 A The Physics of the Plastic Flying Disc 69
18 B Training a Dog to Catch a Flying Disc 71
19 A World Population Growth and Its Effects 73
19 B Megacities 75
20 A The Relationship of Mathematics to Astronomy and Physics 77
20 B The Scientific Method 79
21 A Weather Forecasting Tools 81
21 B Making a Hygrometer 83
22 A The Machine Age in the United States 85
22 B Machines in the Home 87
23 A The History of Space Exploration 89
23 B Tracking Space Missions 91
24 A The Invention of Television 93
24 B The Future of Television 95
25 A Learning About the Ocean 97
25 B The Future of the Ocean 99
附录 101
Answer Key 101
Reading Rate 103
Comprehension Score 104
Comprehension Skills Profile 105