The correct answer is D) By the Rescue Coordination Center (RCC) controlling the distress communications on that frequency or channel. The Rescue Coordination Center (RCC) is responsible for coordinating and directing search and rescue operations, which includes imposing radio silence on the distress frequencies or channels being used. This allows the RCC to maintain control over the distress communications and ensure the integrity of the rescue operation. The other options (A, B, C) do not have the authority or responsibility to impose radio silence in a distress situation, as that is a function specifically handled by the RCC.