地西泮药理作用除外（）
A.镇静
B.催眠
C.中枢性肌松
D.麻醉
E.抗惊厥
参考答案：D
The students enjoy _________ English songs after class.
A．practice to sing
B．practicing singing
C．to practice singing
D．to practice to sing
简述面向对象的三个基本要素。
