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问题 单项选择题

有关域名系统的论述不正确的有（）。

A.IP地址是用四个字节的数字来表示因特网上主机的地址

B.IP地址由网络标识和主机标识两部分组成

C.IP地址中A类级别比B类高

D.把域名翻译成IP地址的软件为DNS

答案

参考答案：C

选择题

某物质和水反应只生成NaOH和O2，则该物质中

A．只含有氧元素

B．一定含有钠元素和氧元素

C．只含有钠元素

D．一定含有钠元素，可能含有氧元素
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单项选择题

Applications put computers to practical business (67) , but below the (68) it’s the heart of an operating system-the kernel-that provides the technical wizardry to juggle multiple program, connect to networks and store (69) .
A traditional kernel provides all the functions for applications. The kernel (70) memory, I/0 devices and parcels out processor time.
The kernel also supports security and fault (71) , which is the ability to recover automatically when parts of the system fail.

A．earth

B．bottom

C．table

D．surface
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