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问题 单项选择题

按照C语言规定的用户标识符命名规则,不能出现在标识符中的是【 】。

A．大写字母

B．连接符

C．数字字符

D．下划线

答案

参考答案：B

解析：在C语言中,用户标识符命令规则规定：变量名只能由字母、数字或下划线3种字符组成,且第一个字符必须为字母或下划线。在C语言中,大写字母和小写字母被认为是两个不同的字符。据此规定A)、D)、C)三个选项是正确的,而B)选项是连字符,不在C语言规定的命名变量标识符的范围内。

完形填空
Directions: Complete the following passage by using the words in the box. Each word can only be used once. Note that there is one word more than you need.
A. fast                B, stuntmen              C. training                D. catching               E. fall
F. seriously       G. really                    H. profession            I. fight                         J. living
You are watching a film in which two men are having a fight. They hit one another hard. At the start, they only __41__ with their fists. But soon they begin hitting one another over the heads with chairs. And so it goes on until one of the men crashes through a window and falls thirty feet to the ground below. He is dead! Of course he isn’t __42__ dead. With any luck he isn’t even hurt. Why? Because the men who fall out of high windows or jump from __43__ moving trains, who crash cars of even __44__ fire, are professionals. They do this for a living. These men are called __45__. That is to say, they perform tricks. There are two sides to their work. They actually do most of the things you see on the screen. For example, they fall from a high building. However, they do not __46__ on to hard ground but on to empty cardboard boxes covered with mattress(床垫). Again, when they hit one another with chairs, the chairs are made of soft wood and when they crash through windows, the glass is made of sugar! But although their work depends on trick of this sort, it also requires a high degree of skill and __47__. Often a stuntman’s success depends on careful timing. For example, when he is “blown up” in a battle scene, he has to jump out of the way of the explosion just at the right moment.
Naturally stuntmen are well paid for their work, but they lead dangerous lives. They often get __48__ injured and sometimes killed. A Norwegian stuntman, for example, skied over the edge of a cliff a thousand feet high. His parachute(降落伞) failed to open, and he was killed. In spite of all the risks, this is no longer a __49 __ for men only. Men no longer dress up as women when actresses have to perform some dangerous action. For nowadays there are stuntgirls, too.
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解答题
先化简（
a2
a-2
-
4
a-2
）•
1
a2+2a
，再选一个你喜欢且能使分式有意义的实数求出分式的值．
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