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问题 单项选择题

A．串是一种特殊的线性表

B．串的长度必须大于0

C．串中元素只能是字母

D．空串就是空白串

答案

参考答案：A

解析： 串是一种特殊的线性表。串的长度不一定非要大于0，如空中；串中元素除了字母外，也可以是数字、符号等；空串是不包含任何字符、长度为0的串，而空白串是包含空白字符(如空格、制表符等)的串，空白串的长度＞0。

改错题

短文改错

I've really got to do something to lose weight because

I'm getting much too fat. I wasn't worried about it until I go

1._________

to see the doctor. He told me that I'd probably had a heart

2._________

attack while I started eating less. When you're on a diet you

3._________

have to stop eat too much even though you are always hungry.

4._________

They may be very hard to do and you certainly need a lot

5._________

of will-power to succeed. So I will stay on a health farm for a

6._________

month I won't be able to eat much and so I'li have to stick

7._________

to my diet. I'll also do plenty of exercise, which won't give

8._________

me any harm too. Both the diet and the exercise will

9._________

help me to lose weight and feel more better.                               

10._________
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不定项选择

两球a和b的质量分别为ma和mb、直径分别为da和db（da>db）。将a、b球依次放入一竖直放置、内径为d（da＜d＜da十db）的平底圆筒内，如图所示。设a、b两球静止时对圆筒侧面的压力大小分别为f1和f2，筒底所受的压力大小为F。已知重力加速度大小为g。若所有接触面都是光滑的，则

[ ]

A．F=(ma+mb)g，f1=f2

B．F=(ma+mb)g，f1≠f2

C．mag＜F＜(ma+mb)g，f1=f2

D．mag＜F＜(ma+mb)g，f1≠f2

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