河南省杞县2017高考英语一轮复习 阅读理解训练（五）.doc1 河南杞县 2017 高考英语一轮阅读理解训练(五) 【由北京市丰台区 2014 高考模拟改编】阅读下列短文,从每题所给的 A、B、C、D 四个选项中,选出最佳选项。 Have you ever lo oked t oward the sky ona fall day and witnessed a group of migrating birds ? If so, you probably noted the V-shaped formation of the birds or the birds flying ina ball-like formation. Why do birds fly this way? Many theories have been developed to explain the formation patterns of different types of birds. One theory is that b irds fly in certain formations to take advantage of the laws of nature. The birds know that flying ina V-shaped pattern will save energy. Like the lead cyclist ina race who decreases wind force for the cyclists who follow, the lead bird cuts wind force for the birds that follow. This decrease in wind force means that the birds use up to 70 percent less energy during their flight. When the lead bird es tir ed, a more rested bird takes over that position. But saving ene rgy is important for more than one reason. Sometimes food is short during migration flights. Keep ing energy enables the birds to fly longer distances between meals. When food is sight ed, the birds guide one another ina different way. When a bird identifies a familiar feeding area, it might turn around in order to signal the group to change direction. Then , this bird es the new leader. It helps guarantee that other birds will know exactly where it is going. Then the whole group makes a cha
