Increasing the number of slack liquid tanks has the effect of raising the __________.

Correct Answer: Option B — virtual height of the center of gravity

Free surface effect occurs when liquid in a tank is free to shift, creating a virtual rise in the center of gravity (KG). This reduces the vessel's effective metacentric height (GM), thereby decreasing initial stability. Increasing the number of slack tanks compounds this virtual rise, significantly compromising the ship's righting arm.