Final answer:
A documentary credit (letter of credit) completely eliminates the risk of nonpayment by an importer or a bank in an international transaction.
Step-by-step explanation:
The option that completely eliminates the risk of nonpayment by an importer or a bank in an international transaction is documentary credit (letter of credit). A letter of credit is a financial document issued by a bank on behalf of a buyer, guaranteeing payment to the seller as long as certain conditions are met. This provides security and assurance to both the exporter and the importer, ensuring that payment will be made.