【单选题】
MAC 层采用了完全确认的(___,每个发送的数据包都必须等待接受方的确认信息。
A. 数据传输机制
B. 自组织功能
C. 碰撞避免机制
D. 自愈功能
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答案
A
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数据库的特点之一是数据共享,严格地讲,这里的数据共享指(___。
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C.计算机技术 D.数据安全技术14230.在关系运算中,选择运算是___。
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