______处于中层，反映了设计者的数据全局逻辑要求。A．概念模式 B．内模式 C．

患儿，4岁半，因前牙外伤1天就诊。检查见右上A冠折，露髓，探痛明显，叩（+）。

如果患儿合作，应该选择的治疗为（）

A.拔除

B.行活髓切断术

C.行Vitapex根管充填治疗

D.直接盖髓

E.观察，暂不处理

X62W铣床的主电路由电源总开关QS、熔断器FU1、接触器KM1～KM6、热继电器FR1～FR3、（）、快速移动电磁铁YA等组成。

A、位置开关SQ1～SQ7

B、电动机M1～M3

C、按钮SB1～SB6

D、速度继电器KS

某投资者在5月份以5.5美元/盎司的权利金买入一张执行价格为430美元/盎司的6月份黄金看跌期权，又以4.5美元/盎司的权利金卖出一张执行价格为430美元/盎司的6月份黄金看涨期权，再以市场价格428.5美元/盎司买进一张6月份黄金期货合约。那么，当合约到期时，该投机者的净收益是( )美元/盎司。(不考虑佣金)

A．2.5

B．1.5

C．1

D．0.5

下列现象中，物质的密度发生变化的是（　　）

A．一杯水倒掉一半

B．一铁块热胀冷缩

C．一块玻璃打碎了

D．粗铜丝变成细铜丝

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 weather Bureau 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 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.

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.

The thirty-day forecast is determined by examining（）

A. upper air levels

B. satellite reports

C. changing fronts

D. daily air maps