(67)A.完整性 B.并发控制

　　C.隔离性 D.安全性

　　● 堆栈和队列的相同之处是__(68)__。

　　(68)A.元素的进出满足先进后出

　　B. 元素的进出满足先进先出

　　C. 只允许在端点进行插入和删除操作

　　D. 无共同点

　　● __(69)__实现传输线上的位流信号同步。

　　(69)A.物理层 B. 数据链路层 C. 网络层 D. 应用层

　　● 采用全双工通信方式，数据传输的方向性结构为__(70)__。

　　(70)A.可以在两个方向上同时传输

　　B. 只能在一个方向上传输

　　C. 可以在两个方向上传输，但不能同时进行

　　D. 以上都错

　　● Electronic mail and filing permit a user to compose and transmit a message on an office __(71)__ system. In the early 1970s, the ARPANET community developed a number of such systems which have been heavily used. Through standard message format __(72)__, several hundred different computers and electronic mail interfaces are specification of how __(73)__ and return addresses should appear on envelopes and which sizes are allowable for envelopes. In the electronic message world, they describe what __(74)__ of characters are required at the __(75)__ of a message to identify the sending and receiving mailboxes.

　　(71)A.robotization B.automation C.dynamic D.action

　　(72)A.protocols B.standards C.rules D.principles

　　(73)A.send B.recipient C.import D.discontinuity

　　(74)A.characteristic B.style C.sequences D.format

　　(75)A.end B.last C.initiation D.beginning