神经细胞每兴奋一次，膜内Na+浓度大约增加（）。 A.1/800 B.1/1000

从地面发射质量为m的导弹，导弹上的喷气发动机可产生恒定的推力，且可通过改变喷气发动机尾喷管的喷气质量和方向改变发动机推力的大小和方向，导弹起飞时发动机推力大小为F=mg，导弹沿和水平方向θ=30°角的直线斜向右上方匀加速飞行。经过时间t后，遥控导弹上的发动机，使推力的方向逆时针旋转60°，导弹依然可以沿原方向匀减速直线飞行。（不计空气阻力和喷气过程中导弹质量的变化）求：

（1）t时刻导弹的速率及位移是多少？

（2）旋转方向后导弹还要经过多长时间到达最高点？

（3）导弹上升的最大高度是多少？

触媒钝性过程中，需注意什么问题？

个体难以做出决定，反复地纠缠某些无意义的问题，害怕他人厌烦自己，有强迫行为很可能是MMPI内容量表中( )的高分特征。

A．焦虑紧张量表
B．强迫固执量表
C．A型行为量表
D．自我力量量表

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 Rearly 75 percent using a simple optical illusion．Butst．ripes,called chevrons(人字形)，painted on ther rads 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 t。repeat Japan’s success．Starting next year，the foundati。n will paint cheyrons and。ther pattems of stripes on selected roads around the country to test how well the patterns reduce highway erashes．

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。ften 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 reallv are but als0 make a lane appear to be narrower．The result is a longer lasting reduction in highway speed and the number of traffic accidents．

The passage mainly discusses（）

A．a new way of highway speed control

B．a new pattern for painting highways

C．a new way of training drivers

D．a new type of optical illusion

根据《电力建设工程施工安全监督管理办法》第十五条，勘察单位在勘察作业过程中，应当（）安全生产技术措施，保证作业人员安全。

A.制定并落实

B.编制

C.严格执行

D.完善