Answer:

Introduction:
In accounting, it is essential to record all the financial transactions of a business to maintain accurate and reliable financial records. The recording of transactions is done in various books of accounts, each serving a specific purpose. For instance, the purchase of stationery by a stationery dealer worth Rs. 5,000 will be recorded in the purchase book.

Purchase Book:
The purchase book is a subsidiary book used to record all credit purchases of goods. It is also known as the purchases journal. This book is primarily used to record transactions related to the purchase of goods for resale or for use in the business. The purchase book is used when goods are bought on credit from suppliers or vendors.

Transaction Recording:
When a stationery dealer purchases stationery worth Rs. 5,000 on credit, it means that the payment is not made immediately, but will be made at a later date as per the agreed terms with the supplier. In this case, the stationery dealer will record this transaction in the purchase book.

Reason for Recording in Purchase Book:
The purchase book is specifically designed to record credit purchases. By recording the transaction in the purchase book, the stationery dealer can keep track of all purchases made on credit. This helps in maintaining accurate and up-to-date records of the inventory and accounts payable.

Other Options:
- Sales Book: The sales book is used to record credit sales made by the business. Since this transaction is a purchase and not a sale, it will not be recorded in the sales book.
- Cash Book: The cash book is used to record all cash transactions, including cash purchases. However, in this case, the stationery dealer made a credit purchase, not a cash purchase.
- Journal Proper (General Journal): The journal proper, also known as the general journal, is used to record miscellaneous transactions that cannot be recorded in any other subsidiary book. Since the purchase of stationery is a specific type of transaction that can be recorded in the purchase book, it will not be recorded in the journal proper.

Therefore, the correct answer is option 'A' - Purchase book.

Correct answer is option A because purchase book records only credit purchase transactions