A.0.5mA B.1mA C.1.5mA D.2mA
A.能開(kāi)放 B.有條件開(kāi)放 C.不能開(kāi)放 D.無(wú)車(chē)可開(kāi)放
A.始端 B.終端 C.始端和終端 D.道岔按鈕