The music of the Classical era reflects the principles of

A. the splendor of the church. B. extravagance and unpredictability. C. clarity and balance. D. ornamentation and extremes.

The music of the Classical era often reflects (and many musical critics and historians of music would agree on this) C - clarity and balance.

Both of these qualities/characteristics can be found if you listen to the music of the Classical era carefully, compared to music that was produced in other time periods.