Which of the following statements about fluorescent lamps is correct? a. The ballast in fluorescent and HID lamps serves as a transformer to boost voltage and a choke to limit the flow of current. b. Fluorescent lamps have positive electrical resistance, meaning that the resistance increases with the flow of current. c. Once an arc is struck in a fluorescent lamp, the ionized mercury vapor reduces its conductivity, limiting the flow of current. d. Fluorescent lamps don't need a higher voltage to initiate the electric arc. e. Fluorescent lamps can be operated without a ballast because they self-limit their current consumption