Why does Jim have a "peculiar expression" on his face when he first comes home in "The Gift of the Magi"?

AHe regrets selling his watch to afford Della's Christmas gift.

BHe realizes that the combs he bought Della for Christmas will be useless now.

CHe regrets not telling Della that he does not want a chain for his watch.

DHe realizes that he's forgotten to buy Della a Christmas gift.