The correct answer is B. Credit note.
A credit note is a document issued by a seller to a buyer to acknowledge the return of goods or the cancellation of a sale. It is used to reduce the amount owed by the buyer to the seller.
A debit note is a document issued by a buyer to a seller to acknowledge the receipt of goods that are not in accordance with the terms of the sale. It is used to increase the amount owed by the seller to the buyer.
A proforma invoice is a document that is sent to a buyer before goods are shipped. It is used to provide the buyer with information about the goods, such as the price, quantity, and delivery date.
A bill is a document that is sent to a customer to request payment for goods or services that have been provided.
In this case, the seller is taking back the sold goods, so the buyer would issue a credit note to the seller.