题目

When coal is burned in a boiler, two kinds of ash by-products are produced: a heavy bottom ash and a fine-as-powder fly ash. About 10 to 15 percent of the coal by-product is bottom ash which is used like sand on streets and highways covered with ice, and also on highways as paving material. It is the fly ash, however, that is receiving much attention. Once considered a waste, fly ash is now regarded as a natural resource in the United States. It can be placed in some lower places, where it is compacted and covered with soil, for the seeds of various grasses and plants to be placed in the soil 2014年12月26日，兰州铁路局 开通兰州至乌鲁木齐首趟动车，这标志着世界一次性建设里程最长的高速铁路全线开通运营．兰新高铁没有经过的地形区是（　　） A、吐鲁番盆地B、青藏高原C、河西走廊D、河套平原