Explanation: A Search and Rescue Transponder (SART) is a type of radar beacon designed to aid in the location of survival craft or vessels in distress. It functions as a *transponder*, meaning it does not transmit continuously. When a SART is activated and placed in the "on" position, it enters a standby mode, listening for radar signals. It will only begin transmitting a distress signal *when it is interrogated by a nearby 9-GHz (X-band) radar*. Upon receiving an X-band radar pulse, the SART immediately transmits a series of 12 sweep signals on the same 9-GHz frequency. These distinctive signals appear as a line of 12 dots on the interrogating vessel's radar display, allowing rescuers to pinpoint the SART's location. Options A and D are incorrect because a SART does not transmit continuously or immediately upon activation or water detection; it awaits interrogation. Option C describes the necessary activation steps, but even once activated, it still requires a radar interrogation to *transmit*.