治疗不稳定心绞痛的药物是
A．开搏通B．地高辛C．肝素D．双氢克尿塞E．硝普钠
参考答案：C
β1受体激动时可引起：
A．胃肠平滑肌收缩
B．心肌收缩力增加，心率加快
C．二者都是
D．二者都不是
--_________ should your robot need_________ batteries?
--Every two months.[ ]
A. How soon, to be changed
B. How long, to change
C. How much, change
D. How often, to change
