可致左心室后负荷过重的疾病是
A．二尖瓣关闭不全B．主动脉瓣关闭不全C．二尖瓣狭窄D．主动脉瓣狭窄E．甲状腺功能亢进
参考答案：D
---How much did you _____ for the book? ---Twenty yuan.
A pay B cost C take D spend
原始生命诞生的摇篮是
A．原始大气
B．原始海洋
C．火山周围
D．土壤表层
