The correct answer is B) list. The difference between the starboard and port drafts of a vessel is called the list. This is because the forces acting on the vessel, such as an uneven distribution of weight or external forces like wind or waves, can cause the vessel to lean or tilt to one side, creating a difference in the water level on the two sides. This is distinct from trim, which is the difference in draft between the forward and aft ends of the vessel. The other options are incorrect because: A) trim refers to the longitudinal difference in draft, not the side-to-side difference; C) heel is the temporary, dynamic tilting of a vessel, usually due to external forces like wind or waves; and D) flotation is the general concept of a vessel's ability to float, not the specific difference in draft between the sides.