电流互感器SF6气体纯度是（）。
A.大于等于95%
B.大于等于97%
C.大于等于98%
D.大于等于99.5%
参考答案：B
Come and see me whenever ______. [ ]
A. you are convenient
B. you will be convenient
C. it is convenient to you
D. it will be convenient to you.
我们可以理解为四象就是春夏秋冬的象征。
