新三民主义能够成为实现国共合作、推动国民革命运动的政治基础，主要是因为新三民主义（）

请你解释和解答下列问题：

（1）小李用一只f=5cm 的放大镜来观察地图中的a 点时，可以看到a 点清晰放大的像．

他说a 点离透镜的距离是5cm．

他的说法不正确，请你将错误之处圈出来，并在其下方改正．

（2）黑箱内有一只焦距为3cm 的凸透镜和一只平面镜，请你画出黑箱内的光路图，并标出平面镜上入射角的度数．

（3）日常生活中能看到的凸面镜有：金属图钉面、______．凸面镜的主要优点是：相同面积的凸面镜比平面镜观察到的范围 ______．

6.02立方分米=______毫升，______千克=8吨50千克．

引起包茎的常见原因不包括（）

A.先天性包皮口狭窄

B.包皮炎症

C.包皮过长并狭窄

D.包皮外伤后粘连

E.阴茎癌

车床小刀架移动对主轴回转轴线若不平行（垂直方向），用小刀架镗内孔时，镗后内孔呈（）。

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.

Workforce is composed of ().

A. both the employed and the self-employed

B. people employed to work for others

C. both employers and employees

D. people available to work and earn incomes