因砷盐对人体有毒，应严格控制，一般规定其限量是
A．百分之二
B．百万分之二
C．0.001%
D．0.01%
E．千万分之五
参考答案：B
We are kept ______ of what is happening in the world by reading newspapers and watching television .
A．reminded
B．informed
C．remembered
D．told
简易的串联型稳压电路至少包含（）。
A.调整管、稳压管、限流电阻
B.调整管、稳压管、限压电阻
C.稳压管、电容、限流电阻
D.稳压管、电容、限压电阻
