[简答题] The vast expanse of the United States of America stretches from the heavily industrialized, metropolitan Atlantic seaboard across the rich flat farms of the central plains, over the Rocky Mountains to the fertile west coast, then halfway across the Pacific to the balmy (温和的) island-state of Hawaii. The American scene awes the viewer with both its variety and size. The continental United States (not counting outlying Alaska and Hawaii) measures, 4,500 kilometers from its Atlantic to Pacific coasts, 2,575 kilometers from Canada to Mexico. The entire nation (all 50 states) covers an area of 9 million square kilometers and has a population of 220 million people. The sparsely settled, far-northern state of Alaska is the largest of America’’s 50 states. It is more than two and a half times the size of Sichuan province. Texas, in the southern part of the country, is second in size. Texas is half the size of Alaska. A land of heavy forests (311 million hectares) and barren desert