Three-tube wheel among seafarers. Class a three tubes. What do you mean by Class A Third Mate? What other levels are there?

Class A (blue cover): captain, first mate, second mate and third mate; Chief engineer, big tube wheel, second tube wheel, third tube wheel. Adapt to the infinite navigation area. Class B (green cover): 1, 3,000 gross tons and above, main propulsion power plant, 3,000 kilowatts and above: captain, first mate, second mate and third mate; Chief engineer, big tube wheel, second tube wheel, third tube wheel. Adapt to the near-ocean navigation area. 2.500 to 3,000 gross tons, main propulsion power plant, 750 to 3,000 kilowatts: captain, first mate, second mate and third mate; Chief engineer, big tube wheel, second tube wheel, third tube wheel. Adapt to the near-ocean navigation area. 3,500 gross tons and above; Main propulsion power plant; 750 kW and above: sailors on duty, mechanics on duty. Adapt to the near-ocean navigation area. Class C (Lake Blue Cover): 1, 3,000 gross tons and above, main propulsion power plant, 3,000 kilowatts and above: captain, first mate, second mate and third mate; Chief engineer, big tube wheel, second tube wheel, third tube wheel. Adapt to the infinite navigation area. 2.500 to 3,000 gross tons, main propulsion power plant, 750 to 3,000 kilowatts: captain, first mate, second mate and third mate; Chief engineer, big tube wheel, second tube wheel, third tube wheel. Adapt to the infinite navigation area. 3,500 gross tons and above; Main propulsion power plant; 750 kW and above: sailors on duty, mechanics on duty. Adapt to the infinite navigation area. Class D (brown cover): 1, gross tonnage below 500 tons, main propulsion power plant below 750 kilowatts: captain, chief officer, second officer, third officer, chief engineer, second officer and third officer. Adapt to the near sea area. Under 2.500 gross tons, main propulsion power plant, under 750 kilowatts: sailors on duty, mechanics on duty. Adapt to the inshore navigation area. Communication category (gray cover): 1, first-class radio electronic member of GMDSS; Adapting to A 1, a 2, a 3, A4 sea area 2, GMDSS level II radio electronic personnel: adapting to A 1, A2, A3 sea area 3, GMDSS general operator: adapting to A 1, A2 sea area or A3, A4 sea area (equipped with two sets of equipment) 4, GMDSS limited operator: adapting to A 1, A2 sea area.

Satisfied, please adopt.