Unit 9 Wheels
第一部分 阅读理解(共两节，满分40分)
第一节(共15小题；每小题2分，满分30分)
阅读下列短文，从每题所给的四个选项(A、B、C和D)中，选出最佳选项。
A
In the 19th century Americans from the eastern states moved out west to settle in the rich new lands along the Pacific Coast.The most difficult part of their trip was crossing the “Great American Desert” in the western part of the United States by horse and wagon.
The western desert can be very dangerous.There is little water and there are few trees.But the desert is also scenery of great beauty.Tall towers of red and yellow stones rise sharply from the fat sandy valley floor.The scene has been photographed many times and appears in movies and on TV.
In Arizona，manmade dams across the Colorado River have made two large lakes in the middle of the dry desert country.At Lake Powell，the red stone arch of Rainbow Bridge rises high above the blue lake.
There are few roads.Many areas of Lake Powell’s shore can only be reached by boat or on foot.But hikers in this empty desert land sometimes find very old native American pictures，painted on the rocks.
In Death Valley，California，the summer temperature rises to 130—165 degrees Fahrenheit.There is less than two
