Final answer:
The true statement concerning the chromatic scale is that it uses all twelve tones in an octave, including both whole tones and semitones, and is not exclusive to any particular type of key.
Step-by-step explanation:
The correct statement concerning the use of the chromatic scale is C) It uses all twelve tones in an octave. The chromatic scale is a musical scale with twelve pitches, each a semitone above or below another. On a piano, this includes all the white and black keys in an octave. It differs from diatonic scales like the major and minor scales, which only use seven of these tones. The chromatic scale does not consist only of whole tones (option A), as it includes both whole tones and semitones. It does not include only natural notes (option B); it encompasses all the notes including sharps and flats. Lastly, the chromatic scale is not exclusive to minor keys (option D); it is used in all types of music regardless of the key or tonality.