The correct answer is D: All these choices are correct. If you receive a report that your audio signal through an FM repeater is distorted or unintelligible, the problem could be: your transmitter is slightly off frequency, your batteries are running low, or you are in a bad location. All three can cause poor audio quality. Being off-frequency causes distortion as the repeater's receiver can't properly demodulate your signal. Low batteries reduce transmitter power and can cause frequency drift. A bad location (poor signal path, multipath, or weak signal) can result in a weak signal that the repeater can't properly receive. For amateur radio operators, checking all three helps diagnose and fix audio quality problems.