Which component is used to adjust the reference voltage?

The component that is typically used to adjust the reference voltage is a frequency-adjusting rheostat. This device allows for fine-tuning of the resistance in a circuit, which directly affects the voltage levels present. By adjusting the resistance, you can modify the voltage that is used as a reference for various applications, ensuring that components like comparators, amplifiers, or control systems function correctly within their intended ranges.

While resistors are also crucial in circuits for establishing voltage levels, a standard resistor does not provide the adjustable capability that a rheostat does. Capacitors are primarily used for filtering and storing energy in the form of electrical charge, while inductors are used to store energy in a magnetic field and are not typically utilized for voltage adjustments. The specific application of the frequency-adjusting rheostat distinguishes it as the correct choice in this context, as it is designed for the dynamic adjustment of voltage levels in a circuit.