Explanation: The gain of a closed-loop operational amplifier (op-amp) circuit is precisely determined by the external components in its feedback network. Op-amps are designed with extremely high internal (open-loop) gain, which is often too high and unstable for practical applications. By implementing negative feedback using external resistors, capacitors, or other components, the overall circuit gain (closed-loop gain) becomes predictable, stable, and significantly lower than the open-loop gain. This external network allows engineers to set the desired amplification ratio for specific tasks, a fundamental concept in amplifier design. Options A, C, and D are incorrect. Maximum operating frequency and load impedance (A) relate to the op-amp's performance limits and stability with a load, not the gain ratio itself. Supply voltage and slew rate (C) affect the maximum output swing and the rate at which the output can change, respectively, but do not directly determine the voltage gain. While op-amps have internal feedback networks (D) that contribute to their open-loop gain characteristics, it is the *external* feedback that shapes and defines the controlled, stable closed-loop gain.