单选题 At 1 January 2003, the balance of Billy Company's Provision for Bad Debts is ＄5,000. At 31 December 2003, the balance of trade debtors is ＄45,000. Billy Company's provision for bad debts equals to 10% of trade debtors. During the year 2003, the bad debt written off is＄2,000. Then Bad Debt expenses of Billy Company this year must be ______. (a)＄2,500. (b)＄1,500. (c)＄-1,500. (d)＄-2,5OO.