化学在生产和日常生活中有着重要的应用。下列叙述正确的是 [ ] A. 氧化铝的熔

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问题:

化学在生产和日常生活中有着重要的应用。下列叙述正确的是 [ ]

A. 氧化铝的熔点很低,不能用于制作耐高温材料

B. 在海轮外壳上镶入锌块,会加快船体的腐蚀速率

C. 硅酸钠的俗名为玻璃,可用于制备硅胶和木材防火剂

D. 氯气是合成塑料、橡胶、人造纤维、农药、染料和药品的重要原料

考点:金属的电化学腐蚀氧化铝硅酸盐氯气
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下图是元素周期表中银元素的信息示意图,对图中信息理解不正确的是

A.该元素为金属元素

B.相对原子质量为107.9

C.元素符号为Ag

D.质子数和中子数均为47

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总义齿修复时,下列手术中不可能增加义齿固位力的是

A.唇颊沟加深术
B.舌系带成形术
C.前庭成形术
D.牙槽嵴重建术
E.上颌结节修整术

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简述膝关节的组成

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Modern industrial society grants little status to old people. In fact, such a society has a system of built-in obsolescence. There is no formal system for continuing our education throughout our life in order to keep up with rapidly changing knowledge. When our education and job skills have grown obsolete, we are treated exactly like those who have never gained an education or job skills and are not encouraged or given the opportunity to begin anew.As a society becomes more highly developed, the overall status of older people diminishes. Improved health technology creates a large pool of old people, who compete for jobs with the young. However, economic technology lowers the demand for workers and creates new jobs for which the skills of the aged are obsolete, forcing older people into retirement. At the same time, young people are being educated in the new technology and are keeping pace with rapid changes in knowledge. Finally, urbanization creates age-segregated neighborhoods. Because the old live on fixed incomes, they must often live in inferior housing. All these factors — retirement, obsolete knowledge and skills, inferior standards of living — lower the status of the aged in society.A century ago, when one could expect to live only to 50 or so, the life span more or less coincided with the occupation and family cycle. But today the average life span allows for fifteen to twenty years of life after these cycles. It appears that our life span is outpacing our usefulness in society.

The high development of economic technology________.

A.makes job skills out of fashion

B.lowers the demand for workers

C.forces old people into retirement

D.creates new jobs for older people

题型:选择题

额外牙常发生在

A.上中切牙之间
B.下切牙之间
C.下颌前磨牙之间
D.上颌侧切牙远中
E.智齿远中

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