参考答案

正确答案：D
解析：此题的问题是："How do day-flying birds find their way?"根据"day-flying"可排除B项。整篇文章讲的是鸟如何确定飞行方向，找到迁徙的正确路线。而鸟是不可能用地图的，文中的"the memory of a map"指的是对地貌的记忆，而非真的地图。只有D项最符合要求。"Day-flying birds may use the sun. If they do so, they must have a precise sense of time. Still others appear to be able to use the earth's magnetic field"。