Which statement about the use of portable electric lights in petroleum product tanks is TRUE?

Correct Answer: Option C — They must be explosion-proof, self-contained, battery-fed lamps.

46 CFR 35.30-20 mandates that portable electric lights used in petroleum tanks must be explosion-proof and self-contained, typically battery-operated. This prevents the risk of ignition from electrical arcing or sparks, which is critical when working in potentially explosive atmospheres containing flammable vapors.