女性，44岁，10年前行二尖瓣闭式扩张，近2年行走时出现胸闷、气促。超声行心动图提示二尖瓣开口面积1.0cm²，瓣膜增厚，钙化，瓣下腱索增粗、融合、缩短。该患者最适合的治疗方法是（）

A.再次闭式扩张治疗

B.球囊扩张治疗

C.直视二尖瓣瓣膜成形

D.药物治疗

E.人工瓣膜置换

When a bridge transmits an Ethernet frame, the Ethernet frame has （）.

A.the broadcast address for the its source address

B.the bridge's LAN address for its destination address

C.the bridge's LAN address for its source address

D.none of the above