克里斯泰勒的( )首次揭示了城市规模等级、空间分布、职能层次等规律。A．中心地学说

如图1所示，真空中相距d=5cm的两块平行金属板A、B与电源连接（图中未画出），其中B板接地（电势为零），A板电势变化的规律如图2所示．将一个质量m=2.0×10^-27kg，电量q=+1.6×10^-19C的带电粒子从紧临B板处释放，不计重力．求

（1）在t=0时刻释放该带电粒子，释放瞬间粒子加速度的大小；

（2）若A板电势变化周期T=1.0×10^-5s，在t=0时将带电粒子从紧临B板处无初速释放，粒子达到A板时动量的大小；

（3）A板电势变化频率多大时，在t=

T

4

到t=

T

2

时间内从紧临B板处无初速释放该带电粒子，粒子不能到达A板．

根据《最高人民法院、最高人民检察院关于办理生产、销售伪劣商品刑事案件具体应用法律若干问题的解释》，以生产、销售伪劣商品犯罪共犯论处的有

A．明知他人实施生产、销售伪劣商品犯罪，而为其提供资金的

B．应当知道他人实施生产、销售伪劣商品犯罪，而为其提供许可证件的

C．明知他人实施生产、销售伪劣商品犯罪，而为其提供生产、经营场所的

D．应当知道他人实施生产、销售伪劣商品犯罪，而为其提供运输、仓储、保管等便利条件的

E．明知他人实施生产、销售伪劣商品犯罪，而为其提供制假生产技术的

挖掘机下坡时（）。

A．可空档滑行

B．可快速行驶

C．应慢速行驶

D．视坡度情况变速驾驶

“凡年满六周岁的儿童，不分性别、民族、种族，应当入学接受规定年限的义务教育”此规定出自于（ ）

A．《中华人民共和国义务教育法》

B．《中华人民共和国宪法》

C．《未成年人保护法》

D．《教师法》

Believe it or not, optical illusion can cut highway crashes.

Japan is a case in point. It has reduced automobile crashes on some roads by nearly 75 percent using a simple optical illusion. But stripes, called chevrons, painted on the roads make drivers think that they are driving faster than they really are, and thus drivers slow down.

Now the American Automobile Association Foundation for Traffic Safety in Washington D.C. is planning to repeat Japan’s success. Starting next year, the foundation will paint chevrons and other patterns of stripes on selected roads around the country to test how well the patterns reduce highway crashes.

Excessive(too great) speed plays a major role in as much as one fifth of all fatal traffic accidents, according to the foundation. To help reduce those accidents, the foundation will conduct its tests in areas where speed-related hazards (danger) are the greatest curves, exit slopes, traffic circles, and bridges.

Some studies suggest that straight, horizontal bars painted across roads can initially cut the average speed of drivers in half. However, traffic often returns to full speed within months as drivers become used to seeing the painted bars.

Chevrons, scientists say, not only give drivers the impression that they are driving faster than they really are but also make a lane appear to be narrower. The result is a longer lasting reduction in highway speed and the number of traffic accidents.

On roads painted with chevrons, drivers tend to feel that（）

A. they should avoid speed-related hazards

B. they are driving in the wrong lane

C. they should slow down their speed

D. they are coming near to the speed limit