The quality of sound is judged by:

The characteristic of sound that lets us distinguish two notes of the same pitch and loudness produced by different sources (for example, the same note played on a flute and a violin) is called the quality or timbre of the sound.

Timbre is determined by the waveform of the sound, which in turn depends on the number of overtones (harmonics) present along with the fundamental, their frequencies, and their relative intensities. A pure tone of a single frequency has a simple timbre, while a sound rich in overtones has a complex, characteristic quality.

Frequency (and the related wavelength) decides the pitch of a sound, not its quality, while amplitude decides its loudness. Therefore, of the choices given, the quality of sound is judged by its various overtones.