Deckhands onboard towing vessels shall be divided into 3 watches when the trip exceeds __________.

Correct Answer: Option D — 600 miles

Regulatory standards under 46 U.S.C. 8104 dictate that deckhands on towing vessels must be divided into three watches for any trip exceeding 600 miles. This mandatory watch-standing structure is a critical safety measure to mitigate the risks associated with crew exhaustion during long-distance towing operations.