The correct answer is B) To prevent the davits from pulling up against the stops. The purpose of an upper limit switch when raising a lifeboat is to automatically stop the lifeboat's upward movement before the davits pull up against the physical stops at the top of the davit's travel. This prevents damage to the davit system and ensures the lifeboat is lowered in a controlled manner. The other answer choices are incorrect - option A would stop the lowering, not the raising, option C does not describe the function of the upper limit switch, and option D is not related to the purpose of this particular safety device.