问题 单项选择题

有效焦点在摄影时增涨的变化规律为

A.管电压越大,焦点越大

B.照射野越小,焦点越小

C.管电流越大,焦点越大

D.曝光时间越长,焦点越大

E.摄影距离越大,焦点越小

答案

参考答案:C

解析:电流越大,焦点越大。

选择题
阅读理解

The earth is our home;we must take Care of it. This means keeping the land,air and water   clean.

Pollution is a dirty word. To pollute means to make things unfit(不合适的)or unclean to use. Pollution comes in many ways. We see it,smell it,taste it and drink it. Pollution is beginning to threaten(威胁)our health,or happiness and our life.

Man. has been polluting the earth from the time he first made fire,washed his clothes in the river and threw his waste on the ground. When land was used up or water became dirty. Men moved to another place. At first the problem was not so serious because there was plenty of clean air,land and water. There weren’t so many people then and their wants(需求)were fewer. All the dirty things could be absorbed(吸收)by nature and soon. covered over(恢复), But this is no longer true. The increase of population(人口增长)and the development of industry have changed that. Man is slowly polluting. his environment.

Through the use of poison(农药),mall has polluted land! killing the animal. By putting dirty water and chemicals into rivers and lakes we have polluted our drinking water,killing the fish.

Our increasing population is part of the problem. More people more waste.

Where is this all to end? Are we turning the world into a big rubbish dump,or is there any hope that we can get rid of(摆脱)the pollution ?Luckily,millions of people have been warned of the danger of pollution. Large numbers of people are now working hard to bring pollution under

小题1:Which sentence is WRONG?

A.We live on the earth,so we should look after it.

B.To pollute means to make air ,water and land unfit for use.

C.All the waste produced by modem industry can be absorbed.

D.Man is now fighting against different kinds of pollution.小题2:In this passage the word "chemicals" means

A.化学

B.化学物质

C.化学的

D.医学的小题3: From the sentences "More people more waste",we know that _______.

A.because of the increase of population and the development of industry,more and more waste is produced

B.we need more people,not more waste

C.there isn’t any hope that we can get rid of the pollution

D.more people have been warned of the danger of more waste.小题4:From the passage we can know that now man_______.

A.doesn’t know how to control pollution

B.still doesn’t realize how serious pollution is

C.is doing something to control pollution

D.begins to understand the pollution