Style is considered less important because all different styles can still make someone feel a similiar way. Substance is more important because art is about how it makes a person feel
The key signature allows the composer to use less accidentals which makes the music less cluttered. Just like the other person who answered this said when a score with multiple instruments is written it is almost always all in the same key to keep the music organized (their answer is better)
The answer is going to be c. hope that helped
