32位的IP地址可以划分为网络号，主机号两部分。以下地址标记中用0表示所有比特为0，用-1表示所有比特为1。其中 (41) 不能作为目标地址； (42) 不能作为源地址； (43) 不能出现在主机之外； (44) 不能出现在本地网之外； (45) 在Ipv4中不用，保留供以后使用。
A．{0，0}
B．{127，主机号}
C．{10，主机号}
D．{网络号，-1}
参考答案：A
解析：网络号0是指本地网络，主机号0是指本地主机，所以{0，0}不能作为目标地址。答案为A。
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| Boffins are the clever ones in class. They always come out __1__ in tests. To be a boffin, you must be good at all the __2__. Boffins are clever, but are never the most __3__ people in the school. They have friends amongst themselves. __14__ in society, they are normally shy and withdrawn (离群的). Boffins __5__ their studies to the __6__ of other people. Edwin is the __7__ example of a boffin. He has friends, but they are also __8__. Edwin is extremely clever. His voice has a very strong British accent that other people __9__ funny. A boffin's interest is something __10__ other people may not be interested in. For example, they may like to play games on computer that others may find __11__. In their spare time, boy boffins __12__ like playing war games and strategies. Boffins prefer technology such as computers to having sports __13__. Normally, they are not very sporty and are bad at __14__. Boffins also act in a manner that is slightly strange. They don't __15__ what other people will think of them because of these outbursts. While most children take the word "boffin" in a __16__ way, adults, especially teachers, __17__ boffins. Boffins spend their time in class actually __18__ attentively instead of messing around. This is mainly the reason why they appear to be more intelligent than everyone else around them. Although they may not be the most exciting people, I like boffins. They have intelligent __19__ of their own and are not afraid to show them. Boffins are the cleverest ones, and there's nothing bad about __20__ in that way. | ||||
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