问题 单项选择题

在区间(-1,1)上任意投一质点,以X表示该质点的坐标.设该质点落在(-1,1)中任意小区间内的概率与这个小区间的长度成正比,则

答案

参考答案:C

解析:[分析] 依题设,X在[-1,1]上服从均匀分布,其概率密度为
[*]
由于[*]
故cov(X,|X|)=0,从而P=0,X与|X|不相关.于是可排除(A)与(B).
对于任意实数a(0<a<1),有[*]
又P{X<a,|X|<a}=P{|X|<a}=a,
从而P{X<a}P{|X|<a}≠P{X<a,|X|<a

多项选择题
阅读理解

阅读理解。

     Michael Jackson is one of the world's best singers. Michael Jackson was born in the middle west of the

city of Gary, Indiana, in 1958. He began singing with his four brothers. They called the group "The Jackson

Five". The group became very popular after appearing on a television program. They started singing in 1965,

and became popular soon. In 1970 the group made their first record with the name of "I Want You Back". It

was very popular. One of their hit records was "Never Say Goodbye".

     Michael was good at dancing as well as singing, for example, his dance moves and moon walking. He was

asked to act in a film in 1978 for the first time, and in the same year he made a record on his own, which sold

eight million copies all over the world.

     Michael nearly didn't go out because he was too famous. Once his fans went off in a faint (晕倒) when

they saw him at the concert. No one can do it by now. He lived in a large house and kept lots of animals. He

never ate meat. He often raised money for Charity. This made him win the Guinness World Records (吉尼斯世界记录) in 2006. He died on June 25th, 2009, but he would live in our heart forever.

1. How many people are there in Michael's group? 

A. Three.

B. Five.

C. Four.

D. Six.

2. What's the name of their first record? 

A. "Never Say Goodbye".

B. "See You, See Me". 

C. "I Want You Back". 

D. "On the World".

3. The underlined word "copies" means _______ in Chinese. 

A. 抄写

B. 张/份

C. 复制

D. 模仿

4. Michael was good at _______ according to the passage. 

A. rock music

B. street dance

C. playing the piano

D. moon walking

5. Why did Michael have to stay at home most of time? 

A. Because he was too famous. 

B. Because he often felt lonely. 

C. Because he had no friends.

D. Because his company asked him to do so.