保安器中真空放电管的作用是当有()时,提供放电径路以保护机械设备。
A、低电压大电流
B、高电压大电流
C、低电压小电流
D、高电压小电流
参考答案:D
阅读理解,判断正(T)误(F)。
Danny and Jenny come to China. Li Ming is their best friend. They want to learn Chinese. They think
China is so great. Winter is coming. Snow is falling. Danny and Jenny like it very much. They play with
snow and make snowmen. They are very happy.
( ) 1. Danny and Jenny are Li Ming's best friends.
( ) 2. They want to learn skiing.
( ) 3. They think China is so great.
( ) 4. They like winter in China.
( ) 5. They are not very happy.
陈旧性心肌梗死患者,心电图示频发室性期前收缩,首选药物是()
A.慢心律
B.普罗帕酮(心律平)
C.奎尼丁
D.β受体阻滞剂
E.钙拮抗剂