Explanation: A mains-operated switching power supply first converts the incoming AC to high-voltage DC using an **input rectifier and filter**. This DC is then fed to an **inverter (chopper)**, which rapidly switches it on and off, creating high-frequency AC pulses. These pulses are applied to a much smaller **output transformer**, which steps down the voltage and provides isolation. The transformer's output is then rectified and filtered by the **output rectifier and filter** to produce the final regulated DC output. A crucial **feedback loop** samples the output voltage and adjusts the inverter's switching action (e.g., duty cycle) to maintain a constant output despite load changes, providing the "output regulation." Option B is incorrect because the inverter (chopper) requires DC input and must come *after* the input rectifier and filter. Option C describes a linear power supply configuration, lacking the essential inverter/chopper for high-frequency switching. Option A is incomplete, missing the final output rectifier and filter stage necessary to produce usable DC.