The correct answer is: D. center of buoyancy
The center of buoyancy is the point at which the buoyant force acts on a body. It is located directly below the center of gravity of the displaced fluid.
The center of gravity is the point at which the entire weight of a body can be considered to be concentrated. It is located at the average position of the mass of the body.
The center of pressure is the point at which the total pressure acting on a surface acts. It is located at the average position of the normal forces acting on the surface.
The metacenter is the point of intersection between the vertical line through the center of buoyancy and the vertical line through the center of gravity of a floating body. It is important in determining the stability of a floating body.