A.1/4~1/2 B.1/4~1/3 C.1/4~3/4 D.1/2~3/4
A.密封良好 B.安裝位置一致、便于觀察 C.接地可靠 D.計數(shù)器調(diào)至“0”值
A.1 B.2 C.3 D.4