A trial balance is a list of balances in the books of a business. It is a statement that shows all the ledger account balances (both debit and credit) of a business in order to check that the total debits are equal to the total credits. The purpose of a trial balance is to detect any errors or omissions made in the double-entry accounting system before preparing the financial statements. Therefore, the correct answer is: "It is a list of balances in the books".