胸腺发育不全（DiGeorge）综合征的表现包括（）

A.高热惊厥

B.低钙惊厥

C.甲状腺功能障碍

D.先天性心血管疾病

E.肝脏功能异常

For（1） 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 （2） for every packet sent. Instead,when a connection is established, a route from the （3）machine to the destination machine ischosen as part of the connection setup and stored in tables inside the（4）That route is used forall traffic flowing over the connection, exactly the same way that the telephone system works.When the connection is released, the virtual circuit is also terminated. With connection-orientedservice, each packet carries an （5）telling which virtual circuit it belongs to.

（1）是（）

A.connectionless

B.connection-oriented

C.datagram

D.telegram