The correct answer is: C. Preventing of Dc mixing with input or output.
Coupling capacitors are used in amplifiers to prevent DC mixing with the input or output signal. This is important because DC can cause distortion in the amplified signal. Coupling capacitors block DC signals while allowing AC signals to pass through. This is because capacitors have high impedance to DC signals and low impedance to AC signals.
Option A is incorrect because coupling capacitors do not limit the bandwidth of an amplifier. The bandwidth of an amplifier is determined by the frequency response of the amplifier’s active components.
Option B is incorrect because coupling capacitors do not match the impedance of an amplifier. The impedance of an amplifier is determined by the impedance of the load connected to the amplifier’s output.
Option D is incorrect because coupling capacitors do not control the output of an amplifier. The output of an amplifier is controlled by the amplifier’s gain.