BZA20110的电流不均衡度为3％，最大的电流差异为（）
A.1.5V
B.3V
C.6V
D.0.75V
参考答案：B
Helen is 15 years old, and Joan is 15, too. So Helen is ____ Joan. [ ]
A. as big as
B. as older as
C. as old as
D. so old as
我国法定计量单位共有几个基本单位？分别是什么？
