The First Americans
There was a time long ago when a land bridge connected Asia and North America. The first settlers in North America crossed this land bridge from what is now Siberia to Alaska. The people who made this initial(最初的) crossing were probably following the animals they used for food. Eventually, the oceans rose and the land bridge between the continents disappeared. The settlers, who I shall call the “First Americans”， could not return to their homeland. _【小题1】
For the next few thousand years, the First Americans migrated（迁徙） south and east throughout North and South America. They made the journey all the way from Alaska to the southern tip of South America, a distance of more than 10, 000 miles. 【小题2】 In the far north, above the Arctic Circle, the First Americans became hunters of the ocean. 【小题3】 In the brief summer，they gathered berries and other plants. In the winter, they stayed in lodges much of the time preparing for the next summer. It was a hard life，but they learned to survive in these harsh conditions.
Farther south, in what is now Arizona, Utah, Colorado, and New Mexico, the First Americans became cliff dwellers(悬崖居民). They began by living in caves that already existed in the cliffs. 【小题4】 The dwellings(住处) they constructed in many ways resembled today's apartment buildings. 【小题5】 They built a system of dams and canals so they could store and use water almost any time of the year. They were so successful that they could raise fruits and vegetables that were not found naturally in the desert. In Mexico and South America, the First Americans founded civilizations that were among the greatest in the world. They built huge pyramids, lived in fabulous cities, and made great advances in science and mathematics long before the Europeans arrived.A．They also discovered foods like corn and potatoes.B．Along the way，they established（建立） many different civilizations.C．The First Americans of the Southwest learned to irrigate（灌溉） the desert.D．They would have to survive in the New World they had discovered.E. They built boats of animal skins and hunted or fished for their food.
F. People living near each other tended to share similar environments and customs.
G. They discovered how to add to the caves by building structures of wood and stone.D
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(答案→)D
解析：本文讲述了最早的美洲人通过大陆桥到达了北美，然而当海平面上升后，大陆桥被淹没，他们只好呆在美洲，再也回不到家乡了，于是他们就慢慢地朝南朝东拓展迁徙，在此过程中，有些人学会了灌溉，有些人学会了狩猎，于是各种文明应运而生了。
【小题1】D根据前句they could not return to their homeland.他们回不去了，和下文对他们生存方式的讲述可以判断D选项能在此起到承上启下的作用，故D选项正确。
【小题2】B根据上文可知他们从最北边的阿拉斯加一直向东向西迁徙，而B选项里面的Along the way在语义上恰好能和上文相衔接，故B选项正确。
【小题3】E前句 the First Americans became hunters of the ocean.讲最初的美洲人成了猎人，而E选项内容恰好与狩猎有关，而且能承接上文，所以E选项正确。
【小题4】G前句They began by living in caves that already existed in the cliffs.他们开始居住在山洞里，纵观选项，只有G选项内容与前句内容相衔接，意思是“他们发现了如何给山洞增加些木头和石头结构。”所以选G。
【小题5】C后句They built a system of dams and canals so they could store and use water almost any time讲述他们是如何储存和使用水的，而C选项内容讲述人们知道如何灌溉，恰好能引出下文，由此判断C选项正确，，