问题 单项选择题 共用题干题

患者45岁,女性,因近2个月来右下后牙不敢咬物,遇冷水及吃甜食酸痛.咬硬物酸软无力,无自发痛史。检查时可见右下颌第一磨牙牙合面釉质部分磨损,牙本质外露,探针探划时某两点酸痛难忍

以下哪一项是最可能引起患牙牙齿松动的原因()

A.牙周膜水肿

B.根尖区骨质破坏吸收

C.颌创伤

D.牙槽骨吸收

E.根尖区压力大

答案

参考答案:A

单项选择题

Some pessimistic experts feel that the automobile is bound to fall into disuse. They see a day in the not-too-distant future when all autos will be abandoned and allowed to rust. Other authorities, however, think the auto is here to stay. They hold that the car will remain a leading means of travel in the foreseeable future.

The motorcar will undoubtedly change significantly over the next 30 years. It should become smaller, safer, and more economical, and should not be powered by the gasoline engine. The car of the future should be far more pollution-free than present types.

Regardless of its power source, the auto in the future will still be the main problem in urban traffic congestion (拥挤). One proposed solution to this problem is the automated highway system.

When the auto enters the highway system, a retractable (可伸缩的) arm will drop from the auto and make contact with a rail, which is similar to those powering subway trains electrically. Once attached to the rail, the car will become electrically powered from the system, and control of the vehicle will pass to a central computer. The computer will then monitor all of the car’s movements.

The driver will use a telephone to dial instructions about his destination into the system. The computer will calculate the best mute, and reserve space for the car all the way to the correct exit from the highway. The driver will then be free to relax and wait for the buzzer (蜂鸣器) that will warn of his coming exit. It is estimated that an automated highway will be able to handle 10,000 vehicles per hour, compared with the 1,400 to 2,000 vehicles that can be carried by a present-day highway.

In an automated highway system, all the driver needs to do is ().

A. keep in the right lane

B. wait to arrive at his destination

C. keep in constant touch with the computer center

D. inform the system of his destination by phone

单项选择题