When the population standard deviation, s , is unknown the sample standard deviation, s, is used in determining the interval estimate for the population mean.（）

A.1770

B.1780

C.1776

D.1790

luding ______.

A) hospitals and medicines

B) schools and students

C) food and manpower resources

D) all of the above

A．variances are equal．

B．population variance is smaller than the sampling distribution varianc

E．

C．population variance is larger than the sampling distribution varianc

E．

D．variances have the same degrees of freedom．

A．an interval estimate

B．a point estimate

C．a statistical parameter

D．a range estimate

nce policy？

A.A prohibition from loading a cargo from a country when the cargo may be a carrier of infectious diseases

B.Arrest of a vessel by legal authorities to satisfy claims through exercise of a maritime lien

C.Damage caused by riot of the population of a port

D.Losses caused by fines from polluting the harbor after malfunction of a piping system

What is the 'biggest city in the world？ That is, (21) city has the largest population？ This seems like (22) question to answer, but actually it isn't.

It's actually rather difficult to say which cities (23) the largest. There are two reasons for this difficulty. First of all, it isn't easy to determine a city's boundaries, that is, where a city ends. Nowadays, nearly all cities have a large (24) area around them. So when we talk about the population of a city, we often mean the population of the whole metropolitan area around the city. That means that it's difficult to determine what the population of a city is because it's difficult to define what a city is.

The second reason that it is difficult to 25 the population of different cities is this: it is almost impossible to get (26) about the population of all cities for the same year. For example, we might get an estimate of New York's population in 1979 and an (27) of Mexico City's population in 1981. So we real ly can't compare the numbers because the information is for (28) different years. And the population of cities changes rather quickly, especially in some cases. For example, the population of Jakarta, Indonesia, may increase by 5% each year, so the population figure will change rather quickly.

So we can say that these are our two (29) for comparing the populations of cities: one, it's difficult to determine the (30) of a city, and two, it is difficult to get accurate information.

21. A. what

B. which

C. where

D. how

DEMAND FOR ELDERLY CARE SERVICES IN CHINA RISING RAPIDLY

The number of elderly people aged above 60 increased.Demand for elderly care services in China will continue to rise due to the increasing aging population.The number of elderly people aged above 60 was over 200 million in 2012, and will be 300 million in 2025 and 400 million in 2034, according to experts.

It will be a tough challenge for China to deal with, due to the increasing rates of urbanization and a DECREASING birth rate.The Chinese people will be facing a big challenge if we do not have enough money when we get older.

The United Nations defines an aging society as one that has 10 percent of its population at or above the age of 60.

When most developed countries were classed as an aging society, their gross domestic product (GDP) per capita stood at between 5,000 to 10,000 U.S.dollars or above.However, China became an aging society in 2001, and its GDP per capita was only 1,000 U.S.dollars.It was 6,000 U.S.dollars in 2012.China’s economic foundation for an elderly society is fragile.

On Sept.13.2013, the State Council issued a guideline to speed up the development of China’s elderly care services, hoping to complete a social care network for its elderly by 2025.

1.What does the word “decreasing” in Paragraph 2 mean？()

A.It means “falling”

B.It means “rising”

C.It means “peaking”

2.What does GDP stands for？()

A.Government Document Publishing Service

B.Gross domestic product

C.General domestic product

3.What was China’s GDP per capita in 2012？ ()

A.It was 1,000 U.S.dollars

B.It was 6,000 U.S.dollars

C.It was 10,000 U.S.dollars

4.Why is China’s economic foundation for an elderly society fragile？()

A.Because of its increasing aging population and its low GDP per capita

B.Because when China was classed as an aging society, our gross domestic product (GDP) per capita is high

C.Because of its decreasing aging population and its high GDP per capita

5.The passage implies that().

A.Chinese government can do nothing to deal with the challenge of the increasing aging population

B.Chinese people don’t need enough money when they get older

C.The Chinese social care network is expected to be completed in the near future"

adequately met？ Sociologists and psychologists are conducting experiments on rats to try to determine the effect of overcrowded conditions on man. Recent studies have shown that the behavior. of rats is greatly affected by space. If rats have adequate living space, they eat well, sleep well, and reproduce well.

However, if their living conditions become too crowded, their behavior. patterns and even their health perceptibly change. They cannot sleep or eat well, and signs of fear and tension become obvious. The more crowded they are, the more they tend to bite each other and even kill each other. Thus for rats, population and violence are directly related. Is this a natural law for human society as well？ Is adequate space not only desirable, but also essential for human survival？

This passage is mainly about ______.

A.living space and behavior

B.population and living conditions

C.interesting experiments on rats

D.a natural law for human society

What is the purpose of the experiments described in the passage？A.To determine how much living space a rat needs.

B.To see what happens when rats live in a limited space.

C.To know the likely effects of inadequate living space on human beings.

D.To find out the relationship between population and living conditions.

How would rats behave when their living conditions become too crowded？A.They eat a lot and become friendly to others.

B.They sleep little and act quite peacefully.

C.They eat little but sleep soundly.

D.They become nervous and tend to be war-like.

The passage suggests that overcrowded conditions ______.A.are directly related with population

B.may cause an increase in violence

C.may lead to high birth rate

D.may bring about pollution problems

请帮忙给出每个问题的正确答案和分析，谢谢！

A．She has completed most of the research that was required for her project．

B．She has not done much research yet and so does not mind changing the focus of her project．

C．She is disappointed that the professor is unfamiliar with her research topiC

D．She believes public schools in the northeastern states were only slightly changed due to immigration．

n. It has been argued that the supply of good land is limited. To feed a large population, inferior land must be cultivated and the good land worked intensively. Thus each person produced less and this means a lower average income that could be obtained with a small population. Other economists have argued that a large population gives more scope for specialization and the development of facilities such as ports, roads and railways, which are not likely to be built unless there is a big demand to justify them.

One of the difficulties on carrying out a world-wide birth control program lies in the fact that official attitudes to population growth vary from country to country, depending on the level of industrial development and the availability of food and raw materials. In the developing country where a vastly expanded population is pressing hard upon the limits of food, space and natural resources, it will be first concern of government to place a limit on the birthrate, whatever the consequences may be. In a highly industrialized society the problem may be more complex. A decreasing birthrate may lead to unemployment because it results in a declining market for manufactured goods. When the pressure of population on housing declines, prices also decline and the building industry is weakened. Faced with considerations such as these, the government of a developed country may well prefer to see a slowly increasing population, rather than one which is stable of declines.

Small population may mean ______.

A．higher productlvity, but a lower average income

B．lower productivity, but a higher average income

C．lower productivity and a lower average income

D．higher productivity and a higher average income