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  3. A weather map is an important tool for geographers. A succession of three or four maps presents a continuous picture of weather

A weather map is an important tool for geographers. A succession of three or four maps presents a continuous picture of weather

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问题    A weather map is an important tool for geographers. A succession of three or four maps presents a continuous picture of weather changes. Weather forecasters are able to determine the speed of air masses and fronts; to determine whether an individual pressure area is deepening or becoming shallow and whether a front is increasing or decreasing in intensity~ They are also able to determine whether an air mass is retaining its original characteristics or taking on those of the surface over which it is moving. Thus, a most significant function of the map is to reveal a synoptic picture of conditions in the atmosphere at a given time.
   All students of geography should be able to interpret a weather map accurately. Weather maps contain an enormous amount of information about weather conditions existing at the time of observation over a large geographical area. They reveal in a few minutes what otherwise would take hours to describe. The United States Weather Bureau issues information about approaching storms, floods, fronts and all climatic conditions in general. Twice a month it issues a 30-day "outlook" which is a rough guide to weather conditions likely to occur over broad areas of the United States. These 30-day outlooks are based upon an analysis of the upper air levels which often set the stage for the development of air masses, fronts, and storms.
   Considerable effort is being exerted today to achieve more accurate weather predictions. With the use of electronic instruments and earth satellites, enormous gains have taken place recently in identifying and tracking storms over regions which have but few meteorological stations. Extensive experiments are also in progress for weather modification studies. But the limitations of weather modification have prevented meteorological results except in the seeding of super-cooled, upslope mountainous winds which have produced additional orographic precipitation on the windward side of mountain ranges. Nevertheless they have provided a clearer understanding of the fundamentals of weather elements.
At the present time, experiments are being conducted in ______.
选项 A、30-day" outlooks"
B、predicting storms
C、controlling weather
D、determining density of pressure groups
答案C
解析 题干experiments are being conducted与原文experiments are in progress同义，由此可判断出本题考查的是对文章第三段第三句话的理解，第三句话Extensive experiments are also in progress for weather modification studies．(人们正在进行大量的实验以研究如何改善和控制天气状况)中 weather modification和controlling weather同义，指按照人的意志和需要来改变天气状况，因此选 [C] 。storms只是各种天气状况中的一种现象，因此排除[B] ；[A] 和[D] 文章未提及。
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