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  3. Considered as a continuous body of fluid, the atmosphere is another kind of ocean. Yet, in view of the total amount of rain and

Considered as a continuous body of fluid, the atmosphere is another kind of ocean. Yet, in view of the total amount of rain and

admin2010-04-12  75
问题     Considered as a continuous body of fluid, the atmosphere is another kind of ocean. Yet, in view of the total amount of rain and snow on land areas in the course of the year, one of the most amazing water facts is the very small amount of water in the atmosphere at any given time. The volume of the lower seven miles of the atmosphere--the realm of weather events--is roughly four times the volumes of the world’s oceans. But the atmosphere contains little water. It is chiefly in the form of invisible vapor, some of which is carried over land by air currents. If all the vapor suddenly fell from the air onto the earth’s surface, it would form a layer only about one inch thick. A heavy rainstorm on a given area may use up only a small percentage of the water from the air mass that passes over. How, then, can some land areas receive more than 400 inches of rain per year? How can several inches of rain fall during a single storm in a few minutes of hours? The answer is that rain-yielding air masses are in motion, and as the driving air mass moves on, new moist air takes its place.
    The basic source of most water vapor is the ocean. Evaporation, vapor transport, and rainfall make up the continuous movement of water from ocean to atmosphere, to land and back to the sea. Rivers return water to the sea. In an underground area of the cycle, flowing bodies of water discharge some water directly into rivers and some directly to the sea.
What might have been discussed in the preceding paragraphs?
选项 A、The ocean.
B、The earth.
C、The rainfall.
D、The atmosphere.
答案A
解析 根据本文的首句的“the atmosphere is another kind of ocean”，以及文章所讲述的大气中的水气如何形成降雨等内容信息，结合篇章知识和信号词another，可以判断，本文之前的内容尽管没有给出，但是推断在此之前讨论的是海水方面的信息，所以选项A是正确的。再从所提供的选项看，首先可以排除的是选项C和D，因为大气和降雨都是本文的内容，而选项B则是降雨的落点，也可排除。故选A)。
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