哪种情况应视为新近感染的活动性结核病，需给予治疗（）

A.三岁以下，结核菌素反应阳性

B.城市居民，成年，结核菌素反应阳性

C.60岁以上，结核菌素反应阳性

D.青壮年发热两周，结核菌素反应阳性

E.以上都不是

Networks can be interconnected by different devices in the physical layer networks can be connected by (71) 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 (72) ，examine the MAC address and forward the frames to a different network while doing minor protocol translation in the process in me network layer，we have routers that can connect two networks，If two networks have (73) network layer，the router may be able to translate betweenthe 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 (74) ．As an example，gateways between Internet e-mail and X，400 e-mail must (75) thee-mail message and change various header fields．

A．reapers

B．relays

C．packages

D．modems