●若关系R与S的(58)，则关系R与S可以执行并、交、差运算。

(58)

●The term, (74) loop, refers to

• ●The term, (74) loop, refers to a loop that is contained within another loop.    (74)A.program
• B.nested
• C.statement,
• D.Network

●The (75)is designed specific

• ●The (75)is designed specifically as a security system for preventing unauthorized communications between one computer network and another computer network.    (75)A.firewall
• B.protocol
• C.hacker
• D.virus

●

• ●A (73) is a named memory block. By using its name, we can refer to the data stored in the memory block.    (73)A.word
• B.record
• C.program
• D.variable

The(71)is

• The(71)is a combination of keys that allows the user to activate a program function without clicking a series of menus options.    (71)A.shortcut-key
• B.quick-key
• C.fast-key
• D.rapid-key

●In computer science ,

• ●In computer science ,a data (72) is a way of storing data in acomputer so that it can be used efficiently.    (72)A.record
• B.file
• C.structure
• D.pool

●

• ●ARP协议属于(69)层，其作用是(70)。    (69)A．传输层
• B．网络层
• C．会话层
• D．应用层    (70)A．由MAC地址求lP地址
• B．由IP地址求MAC地址
• C．由IP地址查域名
• D．由域名查IP地址

●内联网Intr

• ●内联网Intranet是利用因特网技术构建的企业内部网，其中必须包括(68)协议。    (68)A.TCP/IP
• B.IPX/SPX
• C.NetBuilder
• D.NetBIOS

●IP地址块192.168.80.128/27包含了(67)个可用的主机地址。

(67)

• ●IP地址块192.168.80.128/27包含了(67)个可用的主机地址。    (67)A.15
• B．16
• C．30
• D．32

●在HTML文件中，(66)是段落标记对。

(66)

• ●在HTML文件中，(66)是段落标记对。    (66)A.
• B.
• C.

• D.

●对关系S进行(62)运算，可以得到表1；对关系R和S进行(63)运算，可以得到表2。

(62)A．自然连接

B．投影

C．选择

D．并

(63)A．自然连接

B．投影

C．选择

D．并