问题 单项选择题

检测血清中一种微量的小分子肽,下列方法中最敏感的是()。

A.免疫荧光技术

B.放射免疫分析法

C.双向琼脂扩散法

D.单向琼脂扩散法

E.对流免疫电泳

答案

参考答案:B

解析:放射免疫测定法是用放射性核素标记抗原或抗体进行的免疫测定。同位素的高度敏感性使该方法具有重复性好、准确性高等优点。该方法最为敏感,广泛应用于激素等微量物质和CTL功能的检测。故选B。

阅读理解

The world is not only hungry but also thirsty for water. This may seem strange to you, since nearly 70% of the earth’s surface is covered with water. But about 97% of that is sea water or salt water. Man can only drink and use the other 3% of fresh water from rivers, lakes, underground and so on. And we can not even use all of that because some of it has been made dirty.

Earth Day is April 22. But on all other days, we must also remember how important water is. The water that we use is the most important natural resource on the earth. Today we face serious water problems. One of them is water pollution. All kinds of things from cars, factories, farms and homes make our rivers, lakes and oceans dirty. Polluted water is very bad for people to drink. And dirty water is bad for fish, too.

How do cars and factories make our water dirty? First they pollute the air. Then when it rains, the rain water makes our drinking water dirty. Dirty rain, called acid rain is also bad for plants, animals and buildings. Scientists say that in 30 years, more than half of the people in the world won’t have enough clean water. We have to learn how to stop wasting water. One of the first steps is to develop ways of reusing it. Today in most large cities, water is used only once and then sent out into a sewer system (下水道). From there it returns to the sea or goes underground.

But even though every large city reused its water, we would still not have enough. So we should make use of sea water by removing the salt in it. If we can take these steps, fresh water won’t be used up.

小题1:The world is thirsty for water because _______.

A.we don’t have enough fresh water

B.a lot of water goes into sewer systems

C.only 70% of the earth’s surface is water

D.sea water is widely used rather than fresh water小题2:From this passage, we know acid rain _______.

A.is only bad for living things

B.is not bad for buildings and factories

C.can be produced in factories

D.is bad for people, animals, plants and buildings小题3:One difficult way we can solve the problem is to _______.

A.use the water with salt in it

B.remove the salt from sea water

C.get water from underground

D.reuse the water in cities小题4:What is the best title for this passage?

A.Fresh water and sea water

B.A thirsty country

C.The importance of water

D.The world’s water problem

多项选择题