Final answer:
The sixth scale degree of a C harmonic minor scale is A-flat.
Step-by-step explanation:
The sixth scale degree of a C harmonic minor scale is A-flat (Ab). The C harmonic minor scale is built from the notes C, D, E-flat, F, G, A-flat, and B. Since the harmonic minor scale is characterized by raising the seventh scale degree from the natural minor scale, the sixth scale degree remains the same as in the natural minor scale, which in the case of C minor is A-flat.