The exposition of "The Gift of the Magi" is the narrator introducing the young, struggling couple, and the rising action features Della wishing to buy her husband a nice gift. The climax of the story is Della deciding to sell her hair to buy her husband a watch strap. The falling action and resolution is the exchange of gifts, in which Della realizes her husband sold his watch for her gift.
Here are the answers to the given sentences above:-No one answered the ad but me. It is used as PREPOSITION.-There is but one choice to make in this case. It is used as an ADVERB.-Sadie said she would go but she had to bring her sister. It is used as a CONJUNCTION