一个局域网中某台主机的IP地址为176.68.160.12，使用22位作为网络地址，那么该局域网的子网掩码为______。
A．255.255.255.0
B．255.255.248.0
C．255.255.252.0
D．255.255.0.0
参考答案：C
解析： 子网掩码和IP地址一样，也是32bit长，由一串1和跟随的一串0组成。子网掩码中的1对应于IP地址中的网络号net-id和子网号subnet-id，而子网掩码中的0对应于IP地址中的主机号host-id。由于该局域网中使用了22位作为网络地址，因此，子网掩码为11111111.11111111.11111100.00000000，转换成十进制为255.255.252.0。
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| My name is Jim. Our family come 1 America. There are 2 people in my family. My father, my mother and I Now we 3 China. My father is 4 English teacher. He teaches 5 in a middle school. He 6 Chinese quite well. My mother often writes books for the students at home. My father leaves home at ten to six. He begins 7 lesson at 8: 00. He teaches English every day except Sunday. At ten to twelve he finishes his lessons. Then minutes later he has 8 . In the afternoon he often plays games with his students at about four o'clock. Sometimes he teaches his students at his office. Supper time is at about six. After that he 9 newspapers and watches TV. At about ten to eleven he goes to 10 . | |||
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