构成母体的基本*位或元素称为（）。

与产量有明确的技术或实物关系的变动成本（）

A.技术变动成本

B.酌量性变动成本

C.约束性变动成本

D.延期变动成本

下列各句搭配恰当的一句是（　　）

A．根据“一国两制”的构想，我国政府分别同英国、葡萄牙政府达成了解决澳门、香港问题的决议，并于1997年和1999年顺利地进行了 * * 交接。

B．高新科技园区以智力密集为依托，以开拓新产业和高科技成果为目标，不断促进科研、教育与生产相结合。

C．那苗族姑娘看我这样一比一划地，终于明白了我的意思，高兴得笑起来，忙放下背篓，指给我出山的小路。

D．会员家属除凭发出的入场券外，并须有家属徽章，无二者之一即不能入场。

阅读理解。

     Carbon monoxide(一氧化碳) poisoning kills and injures many people and animals around the

world. The gas has been a problem since people first began burning fuels to cook food or to create

heat. It is a problem in all parts of the world that experience cold weather.

     Carbon monoxide is called the silent killer because people do not know it is in the air. The gas

has no color. It has no taste. It has no smell. It does not cause burning eyes. And it does not cause

people to cough. But it is very deadly. It robs the body of its ability to use oxygen.

     Carbon monoxide decreases the ability of the blood to carry oxygen to body tissues. It does this

by linking with the blood. When the gas links with the blood, the blood is no longer able to carry

oxygen to the tissues that need it.

     Damage to the body can begin very quickly from large amounts of carbon monoxide. How

quickly this happens depends on the length of time a person is breathing the gas and the amount of

the gas he or she breathes in.

     Carbon monoxide poisoning has warning signs. But people have to be awake to recognize them.

Small amounts of the gas will cause a person's head to hurt. He or she may begin to feel tired. The

person may feel sick. The room may appear to be turning around. The person may have trouble

thinking clearly. People develop severe head pain as the amount of gas continues to enter their blood.

They will begin to feel very tired and sleepy. They may have terrible stomach pains.

     Medical experts say carbon monoxide affects people differently. For example, a small child will

experience health problems or die much quicker than an adult will. The general health of the person

or his or her age can also be important. An older adult with health problems may suffer the effects

of carbon monoxide more quickly than a younger person with no health problems. People with

heart disease may suffer chest pains. They may begin to have trouble breathing.

1. Why is carbon monoxide called the silent killer?

A. Because it tastes and smells good.

B. Because it is not easily noticed.

C. Because it kills and injures people.

D. Because it always harm people.

2. How does carbon monoxide harm people?

A. It makes people's blood unable to move.

B. It decreases the amount of blood in the body.

C. It makes body tissues full of blood.

D. It makes the blood less able to carry oxygen.

3. When people breathe in small amounts of the gas, they may ________.

A. feel a little dizzy

B. suffer a severe headache

C. go around in the room

D. have a terrible stomachache

4. Which of the following about carbon monoxide poisoning is true?

A. Adults are affected more seriously than children.

B. Young people are more severely affected than old people.

C. People in poor health may have more severe consequences.

D. People with heart problem only suffer from chest pains.

5. The purpose of the passage is to ________.

A. warn people not to burn fuels to keep warm in the winter

B. list the damages that carbon monoxide brings to people

C. give advice on how to avoid carbon monoxide poisoning

D. introduce some knowledge about carbon monoxide poisoning

试述网上书店开设工作程序。

天然气主要有哪些优点（）？

A．绿色环保

B．经济实惠

C．安全可靠