The correct answer is D) to each side of the vessel. The reasoning for this is that the international shore connection must be located to provide access on each side of the vessel, in case the vessel needs to connect to a shore-based firefighting system on either side. This ensures the connection can be made regardless of the vessel's orientation or the location of the shore-based system. The other options are incorrect because they do not ensure access on both sides of the vessel, as required by the relevant regulations.