Explanation: Vessels normally call other ship stations on internationally recognized distress and calling frequencies. For MF/HF radiotelephony, this is 2182 kHz. For VHF radiotelephony, it is Channel 16 (156.8 MHz). Ship stations are required to maintain a watch on these frequencies, making them the primary means for initial contact. Once contact is established, stations typically switch to a designated working frequency to avoid cluttering the calling channel. However, if a station already knows the specific working frequency the other vessel is monitoring, they may call directly on that channel. * **A) Incorrect:** This is too restrictive, as it omits VHF Channel 16, which is widely used for intership communication, and 2182 kHz is an international, not region-specific, calling frequency. * **C) Incorrect:** There is no general rule to call at "15 minutes past the hour," nor does it specify the correct calling channels. * **D) Incorrect:** Vessels do not have unique *calling* channels assigned by the FCC for initiating contact with *other* ships; they use internationally agreed-upon common calling frequencies.