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下列关于化学键说法正确的是:  ( )

A．构成单质分子的微粒中不一定含有化学键

B．只含有共价键的物质一定是共价化合物

C．NaCl溶于水破坏了离子键，乙醇溶于水破坏了共价键

D．CaCl2中既有共价键又有离子键

答案

答案：A

稀有气体分子的最外层电子已经达到稳定结构，所以稀有气体单质分子中不存在化学键，A正确。全部由共价键形成的化合物是共价化合物，B不正确。乙醇是非电解质，溶于水化学键不变，破坏的是分子间作用力，C不正确。钙和氯都是活泼的金属和活泼的非金属，形成的化学键是离子键，D不正确。答案选A。

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Questions


·Read the following passage and answer questions.
1. If sustainable competitive advantage depends on work-force skills, American firms have a problem. Human-resource management is not traditionally seen as a central to the competitive survival of the firm of the United States. Skill acquisition is considered an individual responsibility. Labor is simply another factor of production to rent at the lowest possible cost — as much as one buys row materials or equipment.
2. The lack of the importance attached to human-resource management can be seen in the cooperation hierarchy. In an American firm the chief financial officer is almost always second in command. The post of head of human-resource management is usually a specialized job, off at edge of corporate hierarchy. The executive who holds it is never consulted on major strategic decisions and has no chance to move up to Chief Executive Officer. By way of contrast, in Japan the head of human-resource management is central—usually the second most important executive, after the CEO, in the firm’s hierarchy.
3. While American firms often talk about the vast amounts spent on training their work forces, in fact they invest less in the skills of their employees than do either Japanese or German firms. The money they do is also more highly concentrated on professional and managerial employees. And the limited investments on modem training workers are much more narrowly focused on the specific skills necessary to do the next job rather than on the basic background skills that make it possible to absorb new technologies.
4. As a result, problems emerge when new breakthrough technologies arrived. If American workers, for example, take much longer to learn how to operate new flexible manufacturing stations than workers in Germany do (as they do), the effective cost of those stations is lower in Germany than it is in United States. More times is required before equipment is up and running at capacity, and the need for extensive retraining generates costs and creates bottlenecks that limit the speed, with which new equipment can be employed.
5. The result is a slower pace of technological changes. And in the end the skills of the bottom half of the population affect the wages of the top half. If the bottom half cannot effectively staff the processes that have to operated, the management and professional jobs that go with these processes will disappear.

Questions


·For questions, choose the best title for each paragraph from below.
·For each numbered paragraph, mark one letter (A-G) on the Answer Sheet.
·Do not mark any letter twice.
A. The bad effect of poor management on new technologies.
B. The position of human-resource management in corporation hierarchy.
C. The work force — training in American firms.
D. Human-resource management is not important for American firms.
E. How to make American firms become more completive.
F. The importance of worker’s skill.
G. Problems exit in American’s companies.

Paragraph 4: ______
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