The famous professor’s lectures, though ____ informal, are considered far more informative and interesting.

A．occasionally

B．constantly

C．regularly

D．usually

硝酸酯类与β受体阻断药联合应用抗心绞痛的药理依据是二药

A．均使心室容积减小
B．均使心率减慢
C．均使心肌收缩力减弱
D．均缓解冠状动脉痉挛
E．相互拮抗心室压力的改变