A tuning fork of frequency 300Hz will resonate if a sound wave incident on it has what?

For a tuning fork of frequency 300Hz to resonate, a sound wave incident on it must have a frequency of 300Hz.

Resonance occurs when the frequency of the sound wave matches the natural frequency of the tuning fork. At this frequency, the tuning fork will vibrate with the greatest amplitude, producing a louder and more sustained sound.