The typical firewall consists of two packet filters and a (an)

A． router

B． bridge

C． application

D． server

主动脉瓣二叶瓣畸形易并发（）。

A.心律失常

B.二尖瓣脱垂

C.感染性心内膜炎

D.风心病

E.心肌炎