The correct answer is A) Weight, and refrigeration. When loading a container vessel, the key factors to consider are the weight of the containers and whether any containers require refrigeration. The weight of the containers must be properly distributed to maintain the vessel's stability and prevent overstressing the ship's structure. Additionally, any containers carrying refrigerated cargo need to be positioned to ensure proper airflow and temperature control. The other options are incorrect because they do not address the primary concerns when vertically loading a container vessel. Available dunnage and chocking (B) are more relevant for securing and stabilizing general cargo, not containers. Sweat (C) and crushability/inherent vice (D) are not the main factors to consider in this specific container loading scenario.