Explanation: A Search and Rescue Transponder (SART) is designed to be detected by marine radars operating on the 3-cm X-band. When a SAR vessel's radar interrogates the SART, the SART transmits a series of 12 dots that appear on the SAR vessel's radar display. Crucially, the SART unit itself provides a local visual (e.g., flashing light) or audible (e.g., beep) indication to the personnel in the survival craft that it is being interrogated. This immediately informs them that SAR craft are nearby and actively searching with radar. Option A is incorrect because a Satellite EPIRB's strobe light helps SAR visually locate the craft but doesn't change patterns to indicate radar interrogation. Option B is incorrect as the SART's "standby" mode isn't an indication of approaching SAR. Option D is incorrect because while an AIS SART helps with location via AIS, the specific alarm for *radar interrogation* is characteristic of a traditional radar SART, which directly answers the question about radar-based detection.