The correct answer is A) RoRo Carriers. The International Maritime Organization (IMO) requires Cargo Securing Manuals to be maintained onboard RoRo (Roll-on/Roll-off) carriers. This is because RoRo vessels transport various types of cargo that need to be properly secured to prevent shifting during transit, which could compromise the vessel's stability and safety. The Cargo Securing Manual provides guidance on the appropriate methods and equipment for securing different types of cargo on these types of vessels. The other options (B, C, and D) are not required to maintain this specific manual, as the IMO's requirements for Cargo Securing Manuals are primarily focused on RoRo carriers due to the unique cargo loading and securing considerations for this vessel type.