The correct answer is D) You should put more belly in a sail in light airs than in a strong breeze. This is correct because a sail with more belly (curvature) is more efficient for generating lift in light winds, as it creates a greater difference in air pressure between the two sides of the sail. In stronger winds, a flatter sail shape is more efficient to prevent excessive heeling and reduce drag. Increasing the belly in light airs allows the sail to better harness the available wind energy, while reducing the belly in strong winds makes the sail more aerodynamic and stable. The other options are incorrect - A) is not entirely accurate, B) and C) describe ways to adjust the sail shape, but do not address the relationship between sail shape and wind strength.