Which of the following is not a subsidiary book?

The correct answer is "trial balance". A subsidiary book is a book of original entry used to record similar types of transactions. The sales day book and purchases day book are used to record credit sales and credit purchases respectively. The general journal is used to record transactions that do not fit into any of the other subsidiary books. On the other hand, the trial balance is not a subsidiary book. It is a summary of all the accounts in the ledger and their balances at a particular point in time. It is used to check the accuracy of the ledger balances and ensure that debits and credits are equal.