Correct answer is (c) Radar and FLIR (Forward Looking InfraRed)
The explanation is: In the raster mode HUD a video image of the outside world (generated from the FLIR sensors mounted in the aircraft) and the synthetic image of the outside world (generated from radar sensor) are combined to produce an enhanced vision system. The advantages of these enhanced vision system are that it enables the pilot to fly and land the aircraft in very low visibility conditions and in airports without ILS or MLS or for night flying.