题目： Australian Thunderbirds                   1 Paragraph 1 suggests which of the following about images of birds in ancie...

题目： The Fur Trade and Native Americans Soon after Europeans made contact with the aboriginal peoples of North America, known as Native Americans, trading became the focus of ...

题目： Sea Life Adaptations in the Deep Ocean   Marine scientists identify several zones within the ocean's vertical water column, from the sunlit surface to the deep, dar...

Dating the Ancient Egyptian Pyramids   题目：   The first step toward discovering the age of the ancient Egyptian pyramids is to determine for whom they were built. Ea...

题目： Farming in Uruk   The ancient city of Uruk in the southern region of Sumer in the ancient Middle East developed an agricultural system that depended on irrigation to ...

题目： Biological Rhythms     Biologists have identified many types of biological rhythms, including daily, monthly, and annual rhythms. Among many animals, physiologic...

题目： Submerged Plant Life:Surviving Underwater   Whereas a land plant expends a great deal of energy on the production of roots that can forage in the soil for vital water ...

题目： The Emergence of the State Before there was agriculture, people lived in small, loosely organized bands or tribes that hunted for and collected food in the wild. The emerg...

  题目： French Gothic Cathedrals Gothic-style cathedrals, known for their impressive height. pointed arches, and intricate line patterns, are among the most elaborate s...

题目： Day Length and Reproductive Timing in Animals For many animals, producing offspring at a time of year when a maximum amount of food is available is essential. Producing yo...