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

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

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

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

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