连续用药极易产生耐受性的抗心绞痛药物是
A．卡托普利
B．硝苯地平
C．硝酸甘油
D．普萘洛尔
E．维拉帕米
参考答案：C
---- They say Philip’s brother is a billionaire.
---- ____________? He wouldn’t accept any help from his brother, even if it were offered.
A．What if
B．What for
C．So what
D．Forget it
同步信号为锯齿波的晶体管触发电路，以锯齿波为基准，再串入（）以实现晶闸管触发脉冲的移相。
A、交流控制电压
B、直流控制电压
C、脉冲信号
D、锯齿波电压
