问题 选择题

有A,B两种烃,含碳的质量分数相同,关于A和B的叙述中,正确的是[ ]

A.A和B一定是同分异构体

B.A和B不可能是同系物

C.A和B的最简式一定相同

D.A和B各1 mol,完全燃烧后生成二氧化碳的质量一定相等

答案

答案:D

单项选择题
阅读理解

     Believe it or not, optical illusion(错觉) 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(人字形), 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(基金会) 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 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.      

1. 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

2. The underlined word "hazards" probably means ________.

A. accidents    

B. traffic jams      

C. dangers      

D. cases

3. 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 driv