1.EAR GROWS ON MOUSE'S BACK 2.AIR POLLUTION 3.WHAT MADE OUR ANCESTORS WALK UPRIGHT? 4.WHY DO BIRDS SING? 5.WORLD HUNGER 6. SCIENTISTS HELP SAVE PANDAS 7.HEAT TREATMENT TESTED ON AIDS PATIENTS 8. HERMIT CRABS LEARN WHAT NOT TO EAT 9.SHOULD WE MOVE THE MOON? 10.FROGS TAP OUT LOVE TUNES 11.HOW SAFE IS IRRADIATED FOOD? 12.WHERE DO EARTHQUAKES OCCUR? 13.WHAT IS A STAR? 14.SONAR 15.FOSSILS——THE EVIDENCE OF EARLIER HISTORY 16.SOLAR ENERGY 17.WHY IS THERE MORE SEA THAN LAND ON THE EARTH'S SURFACE? 18.THE COMPASS 19. VITAMINS 20.WHEN WAS THE STETHOSCOPE INVENTED? 參考譯文 Key to the Exercises