从中华人民共和国建立到1956年我国经济发展的总体趋势是（ ） A．由经济残破

全胃肠外营养的要求是

A．氮（g）热比为1：（150～200）kcal

B．钾氮之比为5mmol：1g

C．氨基酸与葡萄糖同时滴注

D．定期补充脂肪乳剂

E．葡萄糖供能占总热量的70％

20MnSi钢号的含义是（）。

A、含碳量为0.20%，含锰量小于1.5%、含硅量小于1.5%的低合金结构钢

B、含碳量为2%，含锰量小于1.5%、含硅量小于1.5%的低合金结构钢

C、含碳量为0.02%，含锰量小于1.0%、含硅量小于1.5%的低合金结构钢

D、含碳量为0.20%，含锰量小于1.0%、含硅量小于1.0%的低合金结构钢

关于乳腺癌的描述，正确的是

A．多来源于肌上皮细胞
B．多发生于内上象限
C．男性乳腺不发生癌
D．多数为浸润性导管癌

如果使用OTDR将光纤故障定位在真实位置±0.5的范围内，则光脉冲的宽度应不在于（）。

A.10ns

B.1ns

C.20ns

D.5ns

Workforce is defined as the total number of people who are available to work and earn incomes. The definition includes everyone who is employed or seeking paid employment, so it includes employers and the self-employed.

Although the size of the workforce depends a great deal on the size of the total population, there are several other influences which also affect it. The age distribution of the total population has a very marked effect on the available workforce. If the population has a high proportion of very young people or of those too old to work, then the available workforce would be lower than if there were an evenly spread age distribution. If the population grows rapidly from natural increase, i.e., the number of births greatly exceeds the number of deaths, then as the total population increases, the proportion in the workforce declines

Sometimes a population is described as aging, which means that the birth rate is either falling or growing very slowly, and as people retire from the workforce, there are not enough young people entering it to replace those who are leaving it. The population is top-heavy with older people. So the percentage of the population in the workforce declines when there is either a rapid increase in births or a falling birth rate.

The age distribution of the population has several important effects on the economy. If the population is aging and there is an increase in the number of people retiring without a corresponding increase in the number entering the workforce, this raises the problem of the ability of the economy to provide a reasonable level of social services to the retired group. If the aged are to be cared for in special homes or hotels, finances must be available for that purpose. If the size of the workforce is small relative to the total population, then the government tax receipts are relatively low and either the government has less money available to it or the workforce members have to be taxed more heavily.

It can be concluded from Paragraph 2 that ().

A. a population growth leads to a greater proportion of workforce

B. a large population does not necessarily mean a high proportion of workforce

C. the size of the aged determines the proportion of workforce

D. the proportion of the very young determines the size of workforce