Networks can be interconnected by different devices. In the physical layer, networks can be connected by （66） 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 （67） , 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 （68） 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 two transport connections. Finally, in the application layer, application gateways translate message （69） . As an example, gateways between Internet e-mail and X.400 e-mail must （70） the e-mail message and change various header fields.

A．reapers

B．relays

C．connectors

D．modems

家庭成员的基本情况及分析不包括( )。

A．家庭成员基本情况介绍

B．客户本人的性格分析

C．非同住、同消费老人的收支介绍

D．家庭重要成员性格分析