下列哪项引起左室容量负荷过重（）
A.二尖瓣狭窄
B.二尖瓣关闭不全
C.肥厚型心肌病
D.主动脉瓣狭窄
E.肺动脉高压
参考答案：B
Please pass me the dictionary ______ cover is made of plastics.
A．whose
B．of which
C．that
D．which
发动机进气门为什么要早开、迟关？
