普萘洛尔抗心绞痛的机制在于
A．降低动脉压
B．减弱心肌收缩力
C．抑制肾素分泌
D．降低心肌耗氧量
E．减慢心率
参考答案：A,B,D,E
My parents are out for business and I ______ stay at home. [ ]
A. must
B. have to
C. mustn't
D. haven't to
体质指数（BMI）即身高（米）/体重（千克）的比值。（）
