The correct answer is C) change of trim. The difference between the initial trim and the trim after loading is referred to as the "change of trim." This is because trim refers to the difference in draft between the forward and aft ends of the vessel, and when cargo or ballast is added, it changes the distribution of weight, resulting in a change to the vessel's trim. The other options are not accurate. "Change of draft" (A) refers to the overall change in the vessel's draft, not just the change in trim. "Trim" (B) is the specific term for the difference in draft, not the change in that difference. "Final trim" (D) is the trim after loading, but does not capture the difference between the initial and final trim.