The correct answer is C) readily accessible for use. The reasoning for this is that lifesaving equipment on board a vessel must be stowed in a manner that allows it to be quickly and easily accessed in an emergency situation. Regulations require that this equipment be kept in conspicuous locations and not locked up or otherwise made inaccessible. Having the equipment readily accessible is critical to ensuring the safety of passengers and crew in the event of an emergency. The other answer choices are incorrect because A) keeping lifesaving equipment on the topmost deck at all times is not a requirement, B) locking up the equipment would make it inaccessible, and D) making the equipment inaccessible to passengers would hinder their ability to use it in an emergency.