I ______ along the road when I saw Peter. So we stopped and had a chat.

A．walked

B．was walking

C．would walk

D．had walked

二尖瓣狭窄的主要病理生理改变是（）

A．右房压力负荷过重

B．左房压力负荷过重

C．右室压力负荷过重

D．左室压力负荷过重

E．左室容量负荷过重