一个圆柱体的侧面积是942cm2，体积是2355cm3，它的底面积是______

(三)

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.

The advantage of chevrons over straight, horizontal bars is that the former（）.

A．can keep drivers awake

B．can cut road accidents in half

C．will look more attractive

D．will have a longer effect on drivers

在一密闭烧瓶中注入NO₂，在25℃时建立下列平衡：2NO₂ N₂O₄ △H<0，若把烧瓶置于100℃的沸水中，下列情况：①颜色，②平均相对分子质量，③质量，④压强，⑤密度，其中不变的是（   ）

A．②④

B．③④

C．③⑤

D．①③

下列哪一选项不能用作商业汇票的签章( )

A．乐新发制品有限公司的法人章
B．海派电子股份有限公司的财务专用章
C．力化音像制品有限公司日2岁的法人代表何某的私人印章
D．黑白药品有限公司的业务代表赵某的签名加盖私人印章

施工现场用电工程中，PE线上每处重复接地的接地电阻值不应大于（）。

A.4Ω

B.10Ω

C.15Ω

D.30Ω

为维护软件开发者的合法权益，解决自动保护可能产生的权属纠纷，我国实行了 (10) 。

A．计算机软件著作权登记制度
B．计算机软件标记制度
C．计算机软件商标制度
D．计算机软件产权审查制度