The correct answer is C) full wave rectification. The function of section "B" in the regulated DC power supply illustrated in EL-0085 is to perform full wave rectification. Full wave rectification converts both the positive and negative half-cycles of the AC input into positive half-cycles, resulting in a more stable and continuous DC output. The other answer choices are incorrect because half wave rectification only uses one half of the AC cycle, quarter wave rectification is not a common technique, and short wave rectification is not a standard term in this context.