Air pollution involves the release into the atmosphere【C1】______ gases, finely divided solids, or finely dispersed liquid aero

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问题      Air pollution involves the release into the atmosphere【C1】______  gases, finely divided solids, or finely  dispersed liquid aerosols at rates that【C2】______ the capacity of the atmosphere to dissipate them or to dispose【C3】______ them through incorporation into solid or【C4】______  layers of the biosphere. Air pollution【C5】______ a variety of causes, not all of which are【C6】______ human control. Dust storms in desert areas and smoke from forest and grass fires【C7】______  to chemical and particulate pollution of the air. Forest fires that swept the state of Victoria, in Australia, in 1939 caused【C8】______ air pollution in Queensland, more than 2,000 miles (3,000 kilometres) away. Dust blown from the Sahara has been【C9】______ in West Indian islands. The discovery of  【C10】______ in Antarctica, where they have never been used, suggests the【C11】______  to which aerial transport can carry pollutants from one place to another. Probably the most important natural【C12】______ of air pollution is volcanic activity , which at times【C13】______ great amounts of ash and toxic【C14】______ into the atmosphere. The eruptions of such volcanoes as Krakatoa, in the East Indies, Mt. St. Helens, in Washington, and Katmai, in Alaska, have been 【C15】______ to 【C16】______ climatic changes.
     Air pollution may affect humans directly, causing a smarting of the【C17】______  or coughing. More indirectly, the effects of air pollution are experienced at【C18】______ distances from the source, as, for example, the fallout of tetraethy lead from urban automobile【C19】______ which has been observed in the oceans and on the Greenland ice sheet. Still【C20】______ directly experienced are the possible effects of air pollution on global climates.
【C7】

选项 A、contribute
B、contrive
C、contradict
D、contrast

答案A

解析 本题也是语义题,从上下文可以判断,文章是要表达沙漠地区的沙尘暴和森林和草场火灾造成空气的化学污染和悬浮物污染。题目中的四个选项都是词形相近的词,但是意思相差甚远,选项A con tribute(to)表示“促成…”,为本题正确答案,选项B contrive表示“图谋、设计”,选项C contradict表示“矛盾、抵触”,选项D contrast表示“与…形成对照”。
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