设随机变量X和Y相互独立,都服从正态分布N(0,1/2),则Y−X的方差为()。 A

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问题:

设随机变量X和Y相互独立,都服从正态分布N(0,1/2),则Y−X的方差为()。

A.1-1/π

B.1-2/π

C.1

D.2

E.4

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题型:单项选择题

                                                         Travelling by train

     In Western countries, if people want to travel from a city to another, they would like to take a train.

 Like in China,there are expresses (快车) and locals (慢车) in these countries. Express trains usually

 travel  fast and local trains usually stop at all stops.

     In a special grade (等级) train, there is a kind of compartment (车厢) called Pullman(卧车).There

 are  sofas, tables, chairs and other things in it. People feel more comfortable (舒适的) there. Of course,

 they  will pay more for it.

     When people take a train, they would like to buy return tickets (返程票). If they want to take the

 Pullman, they should book the tickets.

1. If the people in Western countries want to travel from a city to another, they would like to take

   a _____.

   A. plane    

   B. bus 

   C. train

2. Express trains usually travel _____ than local trains.

    A. slower

    B. fast

    C. faster

3. _____ usually stop at all stops.

    A. Express trains

    B. Local trains

    C. Express trains and local trains

4. People feel more comfortable in _____.

    A. special grade train

    B. compartment

    C. Pullman?

5. If people want to take the Pullman, they should _____.

    A. book the tickets

    B. buy return tickets

    C. buy tickets

题型:单项选择题

下列关于法人的表述中,正确的是( )。

A.是自然人和企事业单位的总称

B.具有民事权利能力

C.具有民事行为能力

D.能够独立承担民事责任

E.能够解决和承担民事行为能力

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生物分类的主要依据是(   )等方面的特征。

A.数量

B.等级

C.形态结构和生理

D.大小

题型:单项选择题

5/9 11/9 ( ) 17/3 106/9

A.7/3

B.22/9

C.23/9

D.8/3

题型:单项选择题

溃疡性结肠炎患者使用抗胆碱能药物时可诱发()

A.肠出血

B.肠穿孔

C.结肠癌变

D.中毒性巨结肠

E.肠瘘

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