Early in the story, you'll find a line in which the author uses imagery and repetition to make the setting reflect Della's mood. Which sentence would be good for this and explain why?
The story begins with what becomes a melancholy refrain. Della would like to buy her husband a nice Christmas present, but she only has one dollar and eighty-seven cents.
ONE DOLLAR AND eighty-seven cents. That was all. And sixty cents of it was in pennies.
The narrator repeats the amount of Della's meager savings three more times.
One dollar and eighty-seven cents. And the next day would be Christmas.
Tomorrow would be Christmas Day, and she had only $1.87 with which to buy Jim a present.
Only $1.87 to buy a present for Jim.
The reader can not only visualize the sum of $1.87 in small coins but can also picture Della counting them over and over again, as if she were hoping as if by magic they would amount to a little bit more. This would seem to be a very good way to represent the whole setting and reflect Della's mood. O. Henry must have thought the same, because he repeats more or less the same words four times. The reader understands not only Della's sorrow but her strong motivation to get Jim a really good Christmas present in order to show her love and to give him some enjoyment in life after a long year of working for a miserable twenty dollars a week. Della keeps counting her money because of her motivation, and her motivation will make it credible that she should reach the sudden drastic decision to sell her beautiful long hair.