张平是一个书法爱好者,周围的人都说他的字方折峻丽,骨力劲健,类似历史上的一位书法家,那就是 [ ]
A.王羲之
B.颜真卿
C.柳公权
D.吴道子
答案:C
采用降低供用电设备的有功功率措施,也可以提高功率因数。
Networks can be interconnected by different devices. In the physical layer, networks can be connected by (11) or hubs, which just move the bits from one network to an identical network. One layer up we find bridges and switches, which operate at data link layer. They can accept (12) ,examine the MAC address, and forward the frames to a different network while doing minor protocol translation in the process. In the network layer, we have routers that can connect two networks. If two networks have (13) network layer, the router may be able to translate between the packer formats. In the transport layer we find transport gateway, which can interface between two transport connections. Finally, in the application layer, application gateways translate message (14) . As an example, gateways between Internet e-mail and X.400 e-mail must (15) the e-mail message and change various header fields.
11()
A.repeaters
B.relays
C.packages
D.modems