Networks can be interconnected by different devices．In the physical layer，networks can be connected by (64) or Hubs, which just move the bits from one network to an identical net-work. One layer up we find bridgas and swiehes, which operate at data link layer. They can accept (65) , 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 netwoks. If two networks have (66) network layer, the router may be able to translate between the packet formats. In the transport layer we find transport gateway, which can interface between the two transport connections. Finally, in the application layer, application gateways translate message

(67) . As an example, gateways between Internet e-mail and X.400 e-mail must (68) the e-mail message and change various header fields.

67（）

A．syntax

B．semantics

C．languages

D．format

下列经济业务会引起资产类项目和负债类项目同时减少的是 （ ）。

A．从银行提取现金

B．赊购原材料

C．用银行存款归还企业的银行短期借款

D．接受投资者投入的现金资产