The correct answer is B) maintained in good and serviceable condition. The reason this is the correct answer is that according to U.S. Coast Guard regulations, required lifesaving equipment on existing vessels may be continued in use as long as it is maintained in good and serviceable condition, regardless of the age of the equipment. The regulations do not require automatic replacement or destruction of equipment after a certain time period, as long as it is properly maintained. The other answer choices are incorrect because they do not align with the actual Coast Guard regulations. Options A, C, and D impose arbitrary time-based requirements that are not part of the actual regulations governing lifesaving equipment on existing vessels.