The correct answer is D) Every ton of weight bearing on the blocks acts as if a ton of weight was removed at keel level. This is correct because when a vessel is dry-docked, the weight of the vessel is transferred from the keel to the dry-dock blocks. This effectively reduces the weight of the vessel acting on the keel, which increases the vessel's stability. Essentially, each ton of weight supported by the blocks is equivalent to removing a ton of weight from the keel, resulting in improved stability. The other options are incorrect because they do not accurately describe the stability changes that occur during dry-docking. Option A is incorrect as the stability calculations are based on the vessel alone, not the combined vessel and dock. Option B is incorrect as the stability increases, not decreases, when the dock is pumped out. Option C is incorrect as the vessel's beam for stability purposes remains the same as when afloat.