Journal Proper is the correct answer.

Journal Proper is a subsidiary book used to record non-regular transactions that do not fit into any other specialized books of accounts. It is also known as the General Journal or the Journal. The transactions recorded in the Journal Proper are of a non-regular nature and do not occur frequently.

When a business purchases fixed assets on a credit basis, it is considered a non-regular transaction because it does not happen frequently. Fixed assets are long-term assets that are acquired for use in the business and are not intended for sale. Examples of fixed assets include land, buildings, machinery, vehicles, etc.

When a fixed asset is purchased on a credit basis, it means that the business does not make an immediate payment for the asset but instead agrees to pay the amount at a later date as per the credit terms agreed upon with the supplier.

The purchase of fixed assets on a credit basis is recorded in the Journal Proper because it is not a regular transaction and does not involve cash or bank transactions. The Journal Proper is used to record all non-regular transactions that cannot be recorded in any other specialized books of accounts.

The entry for the purchase of fixed assets on a credit basis in the Journal Proper would typically include the following details:

- Date of the transaction
- Particulars of the fixed asset purchased
- Amount of the purchase
- Name of the supplier or vendor from whom the asset is purchased

The entry would be recorded by debiting the fixed asset account and crediting the accounts payable or supplier's account. This reflects an increase in the value of the fixed asset and an increase in the liability to the supplier.

By recording such transactions in the Journal Proper, the business maintains a comprehensive record of all non-regular transactions and ensures that they are properly accounted for in the financial statements.