设A是n阶矩阵,且Ak=O(尼为正整数),则()。 A.A一定是零矩阵 B.A有不为

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问题:

设A是n阶矩阵,且Ak=O(尼为正整数),则()。

A.A一定是零矩阵

B.A有不为0的特征值

C.A的特征值全为0

D.A有n个线性无关的特征向量

考点:注册土木工程师岩土工程基础知识基础知识
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近来,国际原油价格不断创出新高。为降低对石油的依赖程度,我国乙醇汽油的使用在不断增加,目前,我国已经成为世界第三大生物燃料乙醇生产国。此外,受油价过高影响,美国市场中型汽车的销量持续下滑。据此回答6-7题。

6.高油价推动乙醇燃料的生产与使用表明                            (    )

①价格变动可以调节生产,对生产经营有重要影响

②价格决定生产,某种商品价格越高,从事该商品的生产越少

③一种商品价格上升,消费者将增加对该商品的替代品的需求

④某一商品价格的提高,会使这种商品的互补商品的需求量增加

A.①②       B.②③      C.③④         D.①③   

7.受油价过高影响,汽车销售量下滑。说明                         (    )

①在有互补关系的商品中,一种商品的价格上升,会使另一种商品的需求减少

②一般来说,价格变动会引起商品需求的变动

③一种商品的价格上升,会使该商品的替代品的需求量减少

④市场应该增加汽车的供给

A.①③       B.①②        C.②③       D.③④    

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与鼻咽部前后处于同一平面的是:()

A.额窦

B.筛窦

C.蝶窦

D.上颌窦

E.上门齿

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As the pace of life continues to increase, we are fast losing the art of relaxation. Once you are in the habit of rushing through life, being on the go from morning till night, it is hard to slow down. But relaxation is essential for a healthy mind and body.

Stress is a natural part of everyday life and there is no way to avoid it. In fact, it is not the bad thing it is often supposed to be. A certain amount of stress is vital to provide motivation and give purpose to life. It is only when the stress gets out of control that it can lead to poor performance and ill health.

The amount of stress a person can withstand depends very much on the individual. Some people are not afraid of stress, and such characters are obviously prime material for managerial responsibilities, others lose heart at the first sign of unusual difficulties. When exposed to stress, in whatever form, we react both chemically and physically. In fact we make choice between "flight or fight" and in more primitive days the choices made the difference between life or death. The crises we meet today are unlikely to be so extreme, but however little the stress, it involves the same response. It is when such a reaction lasts long, through continued exposure to stress, that health becomes endangered. Since we can't remove stress from our lives (it would be unwise to do so even if we could), we need to find ways to deal with it.

46. People are finding less and less time for relaxing themselves because _____.

A. they regard working as their greatest enjoyment

B. they believe that work is superior to relaxation

C. they are traveling fast all the time

D. they are becoming busier with their work than ever before

47. According to the author, the most important character for a good manager is his _____.

A. strong will to hold out stress

B. knowing the art of relaxation

C. high sense of responsibility

D. having control over performance

48. Which of the following statements is TRUE, according to the passage?

A. We can find quite a few ways to avoid stress.

B. Stress is always harmful to people's health

C. It's easy to change the habit of keeping oneself busy with work.

D. Different people can bear different amount of stress.

49. In the last sentence of the passage, "do so" refers to _____.

A. "expose ourselves to stress"

B. "find ways to deal with stress"

C. "remove stress from our lives"

D. "establish links between diseases and stress"

50. According to the author, the right attitude toward stress is _____.

A. to avoid it                 B. to try to cope with it

C. to regard it as a vital motivation      D. to find some relaxation  

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组织最高管理者的管理承诺是建立、实施质量管理体系并持续改进其有效性。

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全球通客户积分由()、()组成。其中奖励积分包括()和()两部分。

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