독해/주제 (1) 썸네일형 리스트형 주제 01 The Grand Canyon, a long, narrow gorge in Arizona, is rich in geological history. It record of past plant and animal life also makes it an exciting and invaluable object of study for biologists. Using samples from the two hundred and seventeen miles of the canyon's walls, scientists analyze the building materials that form the earth's surface and study the natural process which have affected the.. 이전 1 다음