问题 多项选择题

下列关于CO的叙述哪项是正确的

A.CO与Hb的亲和力是O2的250倍

B.CO中毒时可妨碍Hb与O2的结合

C.CO中毒时可妨碍O2的解离,使氧解离曲线左移

D.以上三项都错

答案

参考答案:A,B,C

解析:[考点] CO对氧解离曲线的双重作用
A、B、C三项都是正确的,D项否定前三项是错误的。本题设计目的在于提醒应试者审题时要特别仔细。由于CO与Hb的亲和力高(是O2与Hb亲和力的250倍),所以,极低分压的CO就可以阻断Hb分子中O2的结合位点,妨碍Hb与O2的结合。但是,CO还有另外一种作用,当CO与Hb分子中某个血红素结合后,将增加余下的3个血红素对O2的亲和力,使氧解离曲线左移,又妨碍氧的解离。所以CO中毒时既妨碍Hb与O2的结合,又阻碍HbO2的解离,其危害性极大。

阅读理解

阅读理解。

     The motor vehicle has killed and disabled more people in its brief history than any bomb or weapon

ever invented.Much of the blood on the street flows mainly from uncivil behavior of drivers who refuse to

respect the legal and moral rights of others. So the killing on the road may be regarded as a social

problem.

     In fact,the enemies of society on wheels are rather harmless people-just ordinary people acting

carelessly,you might say.  But it is a general truth both of law and common morality that carelessness is

no excuse when one's actions could bring death or damage to others.  A minority of killers go even

beyond carelessness to total negligence (疏忽).

      Researchers have estimated that as many as 80 percent of all automobile accidents can be attributed

to the psychological condition of the driver.  Emotional upsets can distort (扭曲 )  drivers' reactions, slow their judgment, and blind

them to dangers that might otherwise be clear.  The experts warn that it is necessary for every driver to

make a conscious effort to keep one's emotion under control.

        Yet the irresponsibility that accounts for much of the problem is not confined (限制)  to drivers. 

 Street walkers regularly break traffic rules. They are at fault in most vehicle walker accidents;and many

cyclist even believe that they

are not subject to the basic rules of road.

      Significant legal advances have been made towards safer driving in the past few years. Safety

standards for vehicle have been raised both at the point of manufacture and through periodic

road-worthiness inspections. In addition,speed limits have been lowered. Due to these measures,the

accident rate has decreased. But the accident experts still worry because there has been little or no

improvement in the way drivers behave. The only real and lasting solution,say the experts,is to persuade

people that driving is a skilled task requiring constant care and concentration. Those who fail to do all

these things present a threat to those with whom they share the road.

1.  What is the author's main purpose in writing the passage?

A. To show that motor vehicle is a very dangerous invention.

B. To improve understanding between careless drivers and walkers.

C. To discuss traffic problems and propose possible solutions.

D. To remind drivers of the importance of safe driving.

2.  Why does the author mention the psychological condition of the driver in Paragraph Three?    

A. To give an example of the various reasons for road accidents.

B. To show how important it is for drivers to be emotionally healthy.

C. To show some of the inaccurate estimations by researchers.

D. To illustrate the hidden tensions in the course of driving.

3. Which is not mentioned as being responsible for the road accidents?

A. Careless bicycle-riders.              

B. Mindless people walking in the street.

C. Irresponsible drivers.          

D. Irresponsible manufactures of automobiles.

4. Which of the following best shows the author's attitude towards the future without traffic

     accident problems?

A.  Doubtful yet still longing for.            

B.  Happy and rather confident.

C. Surprised and very pleased.                  

D. Disappointed and deeply worried.

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