Explanation: The DSC distress call data directory contains information from vessels that have sent a distress call *to your radio*. It is not a general database of all vessels or a lookup service for routine communication. Therefore, you would not find the MMSI of an arbitrary vessel you wish to call there, making this action ineffective for resolving the problem. Options B, C, and D are all valid methods. Most DSC radios allow direct manual entry of an MMSI during call setup (B). If you obtain the MMSI, you can permanently add it to your radio's address book (C). Finally, the International Telecommunication Union (ITU) publishes maritime directories containing MMSI numbers for many vessels, which can be looked up and then used to initiate a DSC call (D).