根据《YD5189-2010长途通信光缆塑料管道工程施工监理暂行规定》，工程材料进场后，（）等应满足相关标准要求。

A.存放

B.保管

C.消防

D.领取

Networks can be interconnected by different devices. In the physical layer, networks can be connected by. (31) 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 (32) , 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 (33) 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 (34) . As an example, gateways between Internet E-mail and X. 400 e-mail must (35) the e-mail message and change various header fields.

（31）是（）

A.reapers

B.relays

C.connectors

D.modems