患儿男，7岁。反复咳嗽3年余伴气短，进行性呼吸困难1个月。患儿病前无明显诱因，起病隐匿，咳嗽以干咳为主，曾有痰中带血1次，不伴发热。查体：营养不良貌，Hb109g/L，肺部未闻及明显的干湿性啰音，有杵状指。

如果确诊为特发性肺纤维化，其治疗方案的选择应为（）

A.抗生素

B.止咳化痰

C.无特殊疗法

D.手术

E.β受体激动剂的使用

Frame Relay is simplified form of (51) , similar in principle to (52) , in which synchronous, frames of data are routed to different destinations depending on header information.
Packets are routed throught one or more Virtual Circuits known as (53) . Most Virtual Circuits are (54) , which means that the network provider sets up all DLCI connections at subscription time. (55) are also part of the Frame Relay specification. They privide a link that only lasts only as long as the session.

A．DLCIs

B．HDLCs

C．SDLCs

D．DLs