In, "the gift of the magi," della cannot buy jim a gift. which best analyzes how this conflict develops the plot?

I don't know if you have answer choices but:
The conflict develops the plot by causing Della to sell something that means a lot to her to display her love for Jim, however in the story this causes a paradox, due to what Jim bought. The conflict develops the plot by created a paradox, and developing characters and the emotions between them. 
Hope this helps!