Explanation: VHF marine radios operate on a line-of-sight principle. For effective and responsible communication, good operating practice and FCC regulations dictate using the minimum power necessary to establish and maintain reliable contact. For a station only 1 mile distant, 1 watt of power is almost always sufficient for clear, reliable voice communication, day or night. Using higher power (25 watts) for such a short range is unnecessary and undesirable because it increases the potential for interference to other stations, wastes battery power, and doesn't significantly extend range beyond the line-of-sight limitation. Time of day (sunny vs. dark) has no practical effect on VHF marine radio propagation over short, line-of-sight distances. While 1 watt is also appropriate for routine DSC calls, option D incorrectly implies DSC is the method for "routine communications" in this context, which typically refers to voice.