How does ballast affect ship stability?

Ballast plays a crucial role in enhancing a ship's stability by lowering the center of gravity. When ballast is added to the lower part of a vessel, it effectively increases the weight at the bottom, helping to stabilize the ship against rolling and pitching movements caused by waves and wind. This increased weight in the lower portion of the vessel contributes to a lower center of gravity, which makes the ship more resilient against capsizing. A ship with its center of gravity lower relative to its center of buoyancy has a greater righting moment in the event of heeling, thus keeping it upright in rough conditions.

The other options do not accurately reflect the function of ballast in improving a ship's stability, indicating that they don't recognize the fundamental engineering principles behind ship design and safety. In a well-designed vessel, ballast serves an essential purpose in maintaining balance and stability, especially in varying load conditions.