A vessel 79 feet or more in length must be equipped with which type of bilge pump connected to a bilge manifold, unless an exception applies?

Why B is correct

46 CFR §28.255(c) requires each vessel 79 feet (24 meters) or more in length to be equipped with a fixed, self-priming, powered bilge pump connected to a bilge manifold, except as provided in paragraph (f). A portable pump meeting the 2-inch-per-minute standard is a separate provision applicable when the required pump is portable, not a substitute for the fixed requirement on vessels of that length.