Explanation: Digital Selective Calling (DSC) is primarily a signaling system used to automate the initial alerting phase of a distress call. It's designed to quickly get the attention of other stations and shore facilities. Once a DSC Distress alert is received, the subsequent communication, which includes the actual distress message and coordination, takes place on a designated voice (radiotelephone) or data frequency. Therefore, upon receiving a DSC Distress alert, the proper procedure (D) is to set a watch on the radiotelephone Distress and Safety frequency *associated* with the band from which the alert was received. For example, if a VHF DSC alert is received on Channel 70, you would then switch to VHF Channel 16 to listen for the voice distress message. Answers A, B, and C are incorrect because: * (A) Listening on the DSC frequency itself will only allow you to receive more alerts, not the actual voice distress message. * (B) While Ch 16 and Ch 70 are relevant for VHF, the phrase "continuous watch" isn't the specific *response* to an alert, and Ch 13 is not a primary distress frequency. This answer also doesn't account for alerts received on other bands (e.g., HF, MF). * (C) This describes specific equipment and an incomplete action, not the general procedure for responding to a DSC Distress alert.