磁性材料产品在烧成过程中容易出现（）、起泡、开裂等质量问题。

有些疾病仅靠x线检查即能确诊，但除了( )

A．关节脱位

B．关节畸形

C．急性化脓性骨髓炎

D．以上均不是

E．骨折

“振超精神”“振超效率”在全国引起强烈反响。可是许振超总是谦虚地说：“装卸效率是集体协作的结晶，现代化大生产说到底最需要团队协作。仅凭我一个人，就是一身铁又能打几个钉？”这段话告诉我们[ ]

A．集体无论大小，团结才有力量

B．集体的团结可以使个人能力得到充分的发挥

C．集体的团结能形成强大的合力，达到预期的目标

D．集体团结能够完成个人无法完成的任务，战胜个人无法克服的困难

未参与口腔非特异性免疫的细胞（）。

A.粒细胞

B.肥大细胞

C.单核细胞

D.自然杀伤细胞

E.以上都不是

“安全事故隐患”泛指在生产经营活动中导致事故发生的( )。

A．潜藏着的祸患
B．人的不安全行为、物的危险状态和管理上的缺陷
C．各种危险物品以及管理上的缺陷
D．人、机、环境的危险性

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．

On roads painted with chevrons，drivers tend to feel that______.

A．thev 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