The Q of a tuned circuit refers to the property of ___________

The correct answer is C. Selectivity.

The Q of a tuned circuit is a measure of its sharpness of resonance. A high Q circuit has a narrow bandwidth and is therefore more selective than a low Q circuit.

Sensitivity is a measure of how much input signal is required to produce a desired output signal. Fidelity is a measure of how closely the output signal resembles the input signal.

Neither sensitivity nor fidelity are directly related to the Q of a tuned circuit.