Dear Mr. Morrison:
We are delighted to inform you that your short story, "This Old Mule," has won First Prize in the Northwest Writers Contest. A place has been reserved for you and three of your guests at the Northwest Writers' Conference banquet on August 22. Please do us the honor of attending the banquet where your certificate and a check for $100 will be awarded. I offer you my hearty congratulations. Reset Submit Sincerely, Grace Wooten, Secretary Northwest Writers Group

Which words in this short letter best convey its formal tone?
A. "Dear" and "Please"
B. "three" and "check"
C. "inform" and "honor"
D. "short" and "story"