材料中生物种类较多，它们身体结构和功能的基本单位都是（ ） A．细胞 B．组织

如图为固体物质X、Y的溶解度曲线。在温度为t₂℃时分别把质量为a g的X、Y放入100 g水中，下表为对溶液状态的判断以及使不饱和溶液达到饱和采取的措施。其中正确的是

下列行为中，属于增值税征收范围的是( )。

A．供电局销售电力

B．房地产开发公司销售房屋

C．歌舞厅提供娱乐服务

D．咨询公司提供中介服务

Real policemen, both Britain and the United States hardly recognize any resemblance between their lives and what they see on TV—if they ever get home in time. There are similarities, of course, but the cops don’t think much of them.

The first difference is that a policeman’s real life revolves round the law. Most of his training is in criminal law. He has to know exactly what actions are crimes and what evidence can be used to prove them in court. He has to know nearly as much law as a professional lawyer, and what is more, he has to apply it on his feet, in the dark and rain, running down an alley after someone he has to talk to.

Little of his time is spent in chatting to scantily clad ladies or in dramatic confrontations with desperate criminal. He will spend most of his working life typing millions of words on thousands of forms about hundreds of sad, unimportant people who are guilty—or not—of stupid, petty crimes.

Most television crime drama is about finding the criminal; as soon as he’s arrested, the story is over. In real life, finding criminals is seldom much of a problem. Except in very serious cases like murders and terrorist attacks—where failure to produce results reflects on the standing of the police—little effort is spent on searching. The police have an elaborate machinery which eventually shows up most wanted men.

Having made an arrest, a detective really starts to work. He has to prove his case in court and to do that he often has to gather a lot of different evidence. Much of this has to be given by people who don’t want to get involved in a court case. So as well as being overworked, a detective has to be out at all hours of the day and night interviewing his witnesses and persuading them, usually against their own best interests, to help him.

A third big difference between the drama detective and the real one is the unpleasant moral twilight in which the real one lives. Detectives are subject to two opposing pressures: first as members of a police force they always have to behave with absolute legality, secondly, as expensive public servants they have to get results. They can hardly ever do both. Most of the time some of them have to break the rules in small ways.

If the detective has to deceive the world, the world often deceives him. Hardly anyone he meets tells him the truth. And this separation the detective feels between himself and the rest of the world is deepened by the simple mindedness—as he sees it—of citizens, social workers, doctors, law makers, and judges, who, instead of stamping out crime punish the criminals less severely in the hope that this will make them reform. The result, detectives feel, is that nine tenths of their work is reaching people who should have stayed behind bars. This makes them rather cynical.

When murders and terrorist attacks occur the police（）

A. prefer to wait for the criminal to give himself away

B. spend a lot of effort on trying to track down their man

C. try to make a quick arrest in order to keep up their reputation

D. usually fail to produce results

井巷深（长）度大于7m，平硐长度大于20m时，应采用（）。项目施工单位，应配备气体、粉尘（），定期检测井下空气尘、毒和（）含量。

A.自然通风；检测仪器；氧气

B.自然通风；检测仪器；CO₂

C.机械通风；检测仪器；氧气

D.机械通风；检测仪器；CO₂

外形复杂的图形可用（）标注尺寸。

A.坐标形式

B.网格形式

C.任意形式

D.常规形式