在慢性胃炎的发病机制中，与幽门螺杆菌感染无关的因素是（） A.产生胃壁细胞抗体 B.

     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

下列哪项不是强心苷的不良反应（）

A.心率失常

B.胃肠道反应

C.尿量增多

D.神经系统反应

E.黄视、绿视症

传染病发生和流行的三个基本环节是（）、（）（）。

有以下程序：
#include＜string.h＞
main()
char p[]='a', 'b', 'c', q[10]='a', 'b', 'c';
printf("%d%d\n", strlen(p), strlen(q));

以下叙述中正确的是

A) 在给p和q数组置初值时，系统会自动添加字符串结束符，故输出的长度都为3
B) 由于p数组中没有字符串结束符，长度不能确定；但q数组中字符长度为3
C) 由于q数组中没有字符串结束符，长度不能确定；但p数组中字符长度为3
D) 由于p和q数组中没有字符串结束符，故长度都不能确定

关系R(A，B，C)满足下列函数依赖：F=｛B→C，B→A，A→BC｝，关系R的候选关键字为 (3) ，该关键模式属于 (4) 。

A．AB
B．A和B
C．A和BC
D．AC和AB