单项选择题
Most conducting materials such as copper, aluminum, iron, nickel, and tungsten （）.
A.increase in resistance with increased temperature B.increase in resistance with decreased temperature C.decrease in resistance with increased temperature D.increase in conductance with increased temperature
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 （）.
单项选择题 Routine maintenance of lead acid batteries should include （）.
