Concept:A control account is a summary account used to check the accuracy of entries in subsidiary ledgers.Explanation:Control accounts help in checking errors of addition in ledger accounts.They help in locating errors and missing figures by comparing the total balances.They are not used to monitor the cash book.The cash book is monitored separately through bank and cash transactions.Thus, monitoring the cash book is not a purpose of a control account.Answer:D. monitor the cash book