Explanation:

- Understanding Notes in Business Transactions:

- A Credit Note is issued to a customer when goods are returned. It signifies that the customer's account has been credited to reflect the return, essentially reducing their outstanding balance with the seller.

- A Debit Note is used by a buyer to indicate returns to a supplier or to request a correction in the invoice amount.

- A Proforma Invoice is not related to returns but is a preliminary bill of sale.

- Option Analysis:

- Option 1 - Debit Note: Incorrect for this scenario; it's sent by the buyer for returns.

- Option 2 - Credit Note: Correct, as it is the proper document sent to a customer acknowledging returned goods.

- Option 3 - Proforma Invoice: Incorrect; unrelated to returns.

- Option 4 - None of the above: Incorrect, as Option 2 is accurate.

- The correct answer is Credit Note from Option 2.