问题 选择题
下列事件中,概率不为
1
2
的是(  )
A.掷一枚均匀的硬币,反面朝上的概率
B.四张卡片分别标有“1,2,3,4”,抽到标有“3”的卡片的概率
C.6个除颜色个其他都相同的球中有3个白球,2个红球,1个黄球,从中摸一个球,摸到白球的概率
D.全班有50名学生,有一半人生日在上半年,有一半人生日在下半年的概率
答案

A、因为一枚均匀的硬币只有正反两面,所以在投掷时反面朝上的概率为

1
2

B、因为抽卡时只有4种可能,所以抽到标有“3”的卡片的概率

1
4

C、根据概率公式可知,摸到白球的概率是

3
3+2+1
=
1
2

D、因为这些学生的生日只有在上半年和下半年两种可能,所以有一半人生日在下半年的概率是

1
2

故选B.

问答题 简答题
阅读理解

阅读理解

     "Hey, Jenna, do you think we'll still be friends when we're eightytwo?" I asked my friend.

While I waited for Jenna to answer, I started wondering what life would be like without her.

     Suddenly, my thoughts were interrupted. "Of course, we'll still be friends when we're

eightytwo," Jenna announced loudly.

     The next year, in fourth grade, we met Jamie. Since she lived in the same neighborhood as

Jenna and me, the three of us soon clicked into a really tight group of friends. Things couldn't

have been better, and I thought even time couldn't pull us apart, but that is where I was sadly

mistaken.

     The three of us started fighting a lot-and not just small fights where your friend won't return

a CD you let her borrow. Before Christmas, we had a really big fight.  They both said I was

bossy and couldn't keep my mouth closed. I felt helpless and alone.

     I was surprised when Jenna came to my house and gave me a nice Christmas card she had

made for me. I was so sure that she was still disappointed with me, but now I was getting a

really nice card that she even made herself.

     "Wow," I said, breaking the silence as we stood on either side of my front door. "Thanks."

     "Okay... well... I have to go," she said softly.

     The card started off with  "Merry Christmas", but then, farther down the page, it said,  "I am

so glad we're friends. I am sorry about what I said when we were fighting. A fight won't stop us

from being friends. Besides, we said we were going to be friends even when we're eightytwo."

1. Before fourth grade, the author and Jenna________.

A. were strangers

B. were close friends

C. often fought with each other

D. didn't get along well with each other

2. Jenna and Jamie thought the author________.

A. looked after them very well

B. often cheated them

C. didn't help them

D. often ordered them about

3. Why did the author feel surprised when she received a nice Christmas card from Jenna?

A. Because Jenna had never sent her such a nice card before.

B. Because she never thought Jenna still regarded her as a close friend.

C. Because she thought Jenna would come to fight with her again.

D. Because Jenna didn't return her the CD she had borrowed.

4. After the Christmas, the author and Jenna would ________.

A. lose touch with each other

B. go on fighting with each other

C. not speak to each other

D. be close friends again