我国新研制的歼20飞机具有一定的隐身功能，主要是由于飞机的机身 [ ] A.对电

You will never guess ______ when she found herself ranked first in the competition.

A．how she was excited

B．how excited she was

C．she was how excited

D．how excited was she

党参的原植物有（）

A.党参

B.潞党参

C.素花党参

D.川党参

E.管化党参

聚乙烯管也称（）管。

For (21) service，we need a virtual-circuit subnet．Let US see how that works．The idea behind virtual circuits is to avoid having to choose a new (22) for every packet sent．Instead， when a connection is established，a route from the (23) machine to the destination machine is chosen as part of the connection setup and stored in tables inside the (24) ．That route is used for all traffic flowing over the connection，exactly the same way that the telephone system works． When the connection is released．the virtual circuit is also tenninated．With connection-oriented service，each packet carries an (25) telling which virtual circuit it belongs to．

A．connections

B．resources

C．bridges

D．routers

土料碾压筑堤中，压实参数宜通过碾压试验确定，下列哪项不是压实参数。（）

A、铺土厚度

B、压实遍数

C、含水率

D、压实度