On a pilot vessel of less than 20 meters in length engaged on pilotage duty, the lowest of the two vertical all-round masthead lights must be placed at a height of not less than how many meters above the gunwale?

Why A is correct

33 CFR §84.02(i)(ii) requires that on a vessel of less than 20 meters in length, when two or three lights are carried in a vertical line, the lowest shall be placed at a height of not less than 2 meters above the gunwale. The 4-meter minimum applies only to vessels of 20 meters or more per §84.02(i)(i).