【单选题】
下面有3篇短文，每篇短文后有5道题，每题后面有4个选项。请仔细阅读短文并根据短文回答其后面的问题。
{{B}}第一篇{{/B}}
A、weather map is an important tool for geographers.A、succession of three of four maps presents a continuous picture of weather changes. Weather forecasts 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 weatherBureau issues information about approaching storms, floods, frosts, droughts, 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 outlo6ks are based upon an analysis of the upper air levels with 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 orographical precipitation on the windward side of mountain ranges. Nevertheless, they have provided a clearer understanding of the fundamentals of weather elements.
B．satellite reports
C．changing fronts
D．daily air maps
网考网参考答案：A
网考网解析：
本文第二段最后一句明确指出“These 30-day outlooks are based upon an analysis of the upper air levels with often set the stage for the development of air masses，fronts，and storms”，所以本题的正确答案应当为A。 document.getElementById("warp").style.display="none"; document.getElementById("content").style.display="block"; 查看试题解析出处>>
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