Which one of the following statements concerning bad debt expenses is correct? Select one: O a. Under the allowance method, you recognize bad debt expense when account receivables are written off. O b. Under the percentage of receivables method, bad debt expense is the year-end receivables multiplied by the % of uncollectible accounts. Oc. When you collect a previously written off account, you credit bad debt expense. O d. The year end adjusting entry involves a debit to bad debt expense and a credit to allowance for doubtful accounts