( )是中央银行最常用、也是最重要的一种政策工具。
A．不公开市场操作B．公开市场操作C．公开汇率操作D．不公开汇率操作
参考答案：D
A disk scheduling mechanism in an operating system causes the disk arm to sweepback and forth across the disk surface servicing all requests in its path. This is a
A．First Come First Serve
B．Shortest Seek Time First
C．Scan
D．None of the above
根据链路层协议类型，OSPF将网络分为四种类型：广播，非广播，点到点和（）
A.星型
B.总线型
C.分组
D.点到多点
