Which of the following is NOT a reason for changes in a vessel's lightship KG?

The correct choice indicates that improving fuel efficiency through design is not a reason for changes in a vessel's lightship KG (vertical center of gravity). The lightship KG is affected by the weight and distribution of mass within a vessel, and any alterations that physically impact the vessel's structure, weight, or balance will influence this measurement.

When a vessel is modified for improved fuel efficiency, such as through changes in hull design or propulsion systems, this typically does not change the inherent weight or mass distribution that affects the lightship KG. These improvements may lead to a more efficient vessel without altering the actual weight connected to the vessel's lightship characteristics.

In contrast, the other options do cause changes to the lightship KG. Adding approved alterations usually involves modifications that add weight or shift the center of gravity due to structural changes. The accumulation of paint can increase the vessel's weight, thus impacting the KG. Removal of rust and corrosion may reduce weight and could also affect stability calculations related to the center of gravity. Each of these aspects directly affects the overall weight and distribution of mass, which are key factors in determining the lightship KG.