The correct answer is C) have a smaller amplitude of roll in heavy weather. A vessel with a small GM (Metacentric Height) will have a smaller amplitude of roll in heavy weather. This is because a small GM results in a vessel that is more stable and less prone to excessive rolling motions. With a smaller GM, the vessel's natural rolling period is longer, leading to a more gradual and controlled response to wave action, resulting in a smaller amplitude of roll. The other options are incorrect because: A) a small GM leads to a longer rolling period, not a shorter one; B) a small GM actually provides a more comfortable ride for personnel, not an uncomfortable one; and D) a small GM makes the vessel less subject to synchronous rolling, not more.