问题 单项选择题 A1型题

对诊断阵发性房室或房室结折返性心动过速最有意义的是()

A.心律绝对规则

B.颈动脉按摩能增加房室传导阻滞

C.颈动脉按摩能使心率突然减慢

D.颈动脉按摩时心率逐渐减慢,停止后心率复原

E.心率常>160/分钟以上

答案

参考答案:C

解析:发作突发突止是阵发性室上性心动过速的特点,通过刺激迷走神经的方法可使折返机制的心动过速折返通路传导速度减慢,从而使心律失常发作终止。A、B、E等选项也可见于正常人或其他类型心律失常;D为窦性心动过速或自律性房性心动过速的特点。

阅读理解

根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两处为多余选项。

  1   First, the radioactive material must travel from its place of production to the power station. Although the power stations themselves are strongly built’, the .containers used for the transport of the materials are not. 2 Unfortunately, both’ of these may have an effect on the general public, since they are sure to pass near, or even through heavily populated areas.

Second, there is the problem of waste.  3  It is impossible to make these wastes non—radioactive, and so they must be stored in one of the inconvenient ways .that scientists have invented.For example? they may be buried under the ground, or dropped into deserted mines, or sunk in the sea.However, these methods do not ’solve the problem, since an earthquake could easily break the containers.

Third, there may occur the danger of a leak or an explosion at the power station.As with the other two dangers, this is not very likely to take place. However, it can happen.

Separately, these three types of dangers are not a great cause for worry.  5 

A.It is unusual for radioactive materials to be transported across land.

B.There are three separate sources of danger in supplying energy by nuclear power.

C.All nuclear power stations produce wastes that in most cases will remain radioactive for thousands of years.

D.The general public are strongly against the nuclear program. E.So it does not provide a serious objection to the nuclear program.

F.Normally, only two methods of transport are in use, namely road or rail.

G.But when they are taken together, the probability of disaster is extremely high.

单项选择题 B1型题