The correct answer is D) All of the above. This is the correct answer because the U.S. Coast Guard regulations require the visual inspection of a towline: 1) At least once a month, to ensure its continued serviceability 2) Whenever its serviceability is in doubt, to check for any signs of wear or damage 3) In accordance with the manufacturer's recommendation, which may provide specific guidance on the frequency and method of inspection The other options (A, B, and C) are incorrect because they each specify only one of these requirements, when in fact all three should be followed to properly inspect and maintain the towline in a safe and compliant manner.