单项选择题
In a series circuit, which value will remain unchanged at all places in the circuit?（）
A.Voltage B.Current C.Resistance D.Inductance
单项选择题 Most conducting materials such as copper, aluminum, iron, nickel, and tungsten （）.
单项选择题 The function of a rectifier is similar to that of a （）.
单项选择题 Electrical circuits are protected against overheating by means of a/an （）.
