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问题 多选题

在距地面高为h处，以初速度v水平抛出一个物体，在空中运动时间为t，水平位移为x，则下列说法正确的是（　　）

A．其他条件不变，v越大，则t越大

B．其他条件不变，h越大，则t越大

C．其他条件不变，v越大，则x越大

D．其他条件不变，h越大，则x不变

答案

AB、平抛运动的时间由高度决定，高度越大，时间t越大，与初速度无关．故A错误，B正确．

C、高度不变，时间不变，初速度越大，水平位移x越大．故C正确．

D、h越大，平抛运动的时间越长，初速度不变，则水平位移越大．故D错误．

故选BC．

多项选择题

我国“十一五”科技工作要坚持的基本原则包括()。

A.统筹科技创新和制度创新

B.统筹项目、人才、基地的安排

C.统筹安排工业、农业与服务业的科技创新活动

D.统筹军民科技资源

E.统筹主体功能区科技发展
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单项选择题

Throughout the 19th century and into the 20th, citizens of the United States maintained a bias against big cities. Most lived on farms and in small towns and believed cities to be centres of (1) , crime, poverty and moral (2) Their distrust was caused, (3) , by a national ideology that (4) farming the greatest occupation and rural living (5) to urban living. This attitude (6) even as the number of urban dwellers increased and cities became an essential (7) of the national landscape. Gradually, economic reality overcame ideology. Thousands (8) the precarious (不稳定的) life on the farm for more secure and better paying jobs in the city. But when these people (9) from the countryside, they carried their fears and suspicions with them. These new urbanities, already convinced that cities were (10) with great problems, eagerly (11) the progressive reforms that promised to bring order out of the (12) of the city.

One of many reforms came (13) the area of public utilities. Water and sewerage systems were usually operated by (14) governments, but the gas and electric networks were privately owned. Reformers feared that the privately owned utility companies would (15) exorbitant (过渡的) rates for these essential services and (16) them only to people who could afford them. Some city and state governments responded by (17) the utility companies, but a number of cities began to supply these services themselves. (18) of these reforms argued that public ownership and regulation would (19) widespread access to these utilities and guarantee a (20) price.

（10）（）

A.overwhelmed

B.overflowed

C.overtaken

D.preoccupied
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