The correct answer is A) without delay. The reasoning for this is that the regulations governing the Oil Record Book, as per the MARPOL international agreement, require that each operation involving the transfer of oil or oily mixture be fully recorded in the Oil Record Book without delay. This ensures accurate and timely documentation of such operations, which is critical for environmental protection and compliance purposes. The other options are incorrect because they allow for delays in recording the operations, which goes against the regulatory requirement of recording them without delay upon completion.