a. 1.) How many simultaneous observing locations does an epipolar navigation system require? (a) One (c) Three (b) Two (d) Four a.2.) Which of the following devices or systems operates at the lowest frequency? (a) A radar set (c) A photoelectric proximity sensor (b) The GPS (d) A loran system a.3.) Which of the following devices or systems operates on the basis of fluctuating magnetic forces between physical objects? (a) A sonar system (c) A dynamic transducer (b) A loran system (d) A capacitive proximity sensor