Question：The suspense account shows a debit balance of $100.

　　What could this balance be due to?

　　A. Entering $50 received from A Turner on the debit side of A Turner's account

　　B. Entering $50 received from A Turner on the credit side of A Turner's account

　　C. Undercasting the sales day book by $100

　　D. Undercasting the purchases account by $100

　　The correct answer is: Undercasting the purchases account by $100.

　　解析：'Entering $50 received from A Turner on the debit side of A Turner's account' and 'Entering $50 received from A Turner on the credit side of A Turner's account' will only affect the personal ledgers, 'Undercasting the sales day book by $100' will cause an incorrect double entry.