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问题 单项选择题

用均数和标准差可以全面描述以下哪种分布的特征()

A．正偏态

B．负偏态

C．正态

D．任意分布

答案

参考答案：C

解析：均数用于反映对称分布，特删是正态分布或近似正态分布变量的平均水平；标准差用于描述正态分布或近似正态分布变量的离散趋势。因此均数和标准差可以全面描述正态分布变量的分布特征，此题选择C。

阅读理解

阅读理解

     The influenza virus(流感病毒) or the flu is spread from person to person in the air when an infected

person coughs or sneezes.There are 3 types of the flu:

     -Type A viruses can infect people,birds,pigs,horses,seals,whales,and other animals,such as avian flu

or bird flu.

     -Type B viruses infect people and result in smaller outbreaks(爆发). People infected with type B

viruses are often hospitalized with higher death rates.

     -Type C viruses cause mild illness in humans without the onset of an epidemic (流行病).

Most people are familiar with the symptoms of the flu,but they can be mistaken for a severe cold.The flu

infection is far more serious and can cause severe health complications (并发症). There are many viral

infections that can cause flulike symptoms.It is better to visit your doctor so other possibilities can be

ruled out before your obtaining treatment.

     The flu virus attacks the body's cells and changes into different forms,which is why people who have

received the flu shot (流感疫苗接种) may still get ill with the flu.The influenza virus is transmitted_

through direct contact with infected persons such as by inhaling (吸入)droplets when they have coughed

or sneezed.It can also be spread by handling objects such as doorknobs and telephone receivers that an

infected person has been in contact with.

     If you have the flu,get plenty of bed rest and drink lots of fluids.Most people recover from the flu in

one to two weeks.Doctors often recommend flu vaccines( 疫苗) for highrisk groups such as young

children,the elderly,those with chronic(慢性的) diseases,weak immune systems,or professionals working with highrisk groups.

1. Which of the following is true about bird flu?

A. It is a disease which can spread among humans and animals.

B. Only animals and birds but not humans can be infected by this kind of virus.

C. This kind of disease can cause higher death rates among humans.

D. Bird flu won't cause the outbreak of an epidemic among humans.

2. When you cough or sneeze,a proper suggestion given by the writer is to ________.

A. take some medicine at once

B. see a doctor to make sure of the disease

C. drink more water

D. take more exercise and bed rest

3.  Why some people who have received flu vaccines are still down with the flu?

A. Because the flu is not easy to be treated.

B. Because the flu can spread from person to person.

C. Because people are easy to catch cold.

D. Because the flu virus may have different forms.

4. Once you are down with the flu,what should you do?

A. Take flu vaccines.

B. Improve immune systems.

C. Take enough bed rest.

D. Do more physical exercise.

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单项选择题

新中国成立以后，中国戏曲发展的指导方针是什么（）

A、有效改良

B、全面改革

C、继承传统

D、推陈出新
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