What is the significance of the Q factor of a resonant circuit?

The Q factor, or quality factor, of a resonant circuit is significant because it indicates how sharply the circuit resonates at its resonant frequency. A higher Q factor means that the circuit has a narrower bandwidth around its resonant frequency, producing a more pronounced peak in its frequency response. This sharpness of the resonance peak affects how well the circuit can select or "tune into" a specific frequency, making it very important in applications like radio transmitters and receivers where selective frequency tuning is crucial.

In contrast, the other options address different aspects of circuit performance that do not pertain directly to the Q factor. While total current flow, power rating, and frequency response range are important characteristics of a circuit, they do not reflect the sharpness or selectivity of resonance that the Q factor specifically measures. Thus, the correct answer highlights the critical role of the Q factor in defining the resonance behavior of the circuit.