直流电动机有哪些特点？

Is the world too crowded? Well, that’s a hard question to answer. It’s all a matter of perspective(视角).In Montana, you might drive for a mile in any direction and not see another human being. In Macao, 60,000 people live in every square mile!

What is true is that the world’s population doesn’t stay the same. It has been increasing at a very fast rate(比例).That’s in part because in each generation(代) these are more people who then have children than in the last generation.

Five hundred years ago, the population of the world was about 460 million. In 1900,the world’s population was under 2 billion(十亿).Right now it is doubling every 40 years. That means, if this rate of growth continues, when you are a parent, there will be twice as many people on earth as there are now. Wow! Now that’s a whole lot of people! Soon the world’s population will probably reach 7 billion. Some people worry about that! But there is a lot of disagreement about just how many people on earth equals(相当于) too many people. But everyone agrees that the more people there are, the more resources(资源) the world needs to feed, house and take care of all of them, and the more need there is to think carefully about how we live and use the earth’s resources.

小题1:From the first paragraph we can know that ­________.

A．Montana is too crowded

B．Macao is too crowded

C．the world is too crowded

D．the world is not too crowded小题2:The population is increasing fast partly because ________.

A．people live longer than before

B．there are less wars than before

C．medicine is developing faster than before

D．more couples now would like to have children than before小题3:What was the world’s population 100 years ago?

A．450 million.

B．about 2 billion.

C．40 billion.

D．7 billion.小题4:The writer thinks that with the population increasing, we should ________.

A．find more resources

B．use more resources

C．think about our ways of living

D．move to other places小题5:From the passage we can learn that the writer ________.

A．thinks the world already has too many people

B．thinks the world can feed no more than 7 billion people

C．is not sure when the world’s population will reach 7 billion

D．is not sure what the largest population that the world can feed is

生命周期法开发系统强调整体性，采用（）。

A.先确定逻辑模型，再设计物理模型的方法

B.先设计物理模型，再确定逻辑模型的方法

C.确定逻辑模型和设计物理模型同时进行的方法

D.确定逻辑模型的设计物理模型的工作无先后顺序约定

指导左心衰竭治疗最有用的监测指标是（）。

A.中心静脉压

B.心排心量和心排血指数

C.尿量

D.血压

E.肺毛细血管楔压

—What are those?

—______. [ ]

A. These are cars

B. Yes, they are  

C. They are buses

D. No, they are cars

凡属哪些气温下的混凝土施工，均应按低温季节混凝土施工的有关规定执行？