电流互感器有什么等级要求?
参考答案:
常用的电流互感器分为:0.2、0.5、1、3、10共五个级别。
应根据( )和场所特点,选用相应显色指数的光源。
A.识别要求
B.识别清晰度要求
C.识别颜色要求
D.识别材料要求
Robert is away. He _______ America since last week.
A.has been to
B.has joined a club in
C.has studied in
D.has become a manager in