The correct answer is B) with the unit elevated as high as possible. The reason for this is that a SART (Search and Rescue Transponder) unit needs to be elevated as high as possible to achieve the greatest transmission potential. This is because the SART signal is transmitted via radar, and the higher the antenna is, the further the signal can reach and be detected by searching vessels. Keeping the SART elevated maximizes the line-of-sight range and improves the chances of the signal being received by rescue aircraft or ships. The other options are incorrect because: A) having the antenna in the water would not provide an efficient ground and would impair the signal; C) keeping the SART inside the survival craft would block the transmission; and D) activating the SART in the water is not the optimal position for transmission.