Final answer:
The sixth scale degree of a C-sharp harmonic minor scale is A-sharp.
Step-by-step explanation:
The sixth scale degree of a C-sharp harmonic minor scale is A-sharp. In the harmonic minor scale, the seventh degree is raised by a half step from the natural minor scale, but the sixth degree remains the same as in the natural minor. Therefore, starting on C-sharp and moving up the scale, the notes are C-sharp, D-sharp, E, F-sharp, G-sharp, A-sharp, and the raised seventh, B-sharp, before returning to C-sharp an octave higher.