Please explain to me how to do this

Cainas Cookies purchases Supplies on 1/1/16 for $800. Upon a count of the supplies, Cainas determines there are $250 of supplies on hand at 1/31. What entry does she need to make? A. Debit: Supplies $800 and Credit: Cash $800 B. Debit: Supplies Expense $250 and Credit: Supplies $250 C. Debit: Supplies Expense $550 and Credit: Supplies $550 D. Debit: Prepaid Supplies $550 and Credit: Supplies Exp $550