The tone of a story is determined in large part by

Aits mood.
Bits genre.
Cthe author's treatment of the characters in his or her story.
Dthe author's attitude toward the subject upon which she or he writes.

Verified Answer :

The author's attitude toward the subject on which he/she is speaking.

attitude is everything like if you were hanging out with your best friend and your feeling down that just makes everyone else in a bad mood.