Final answer:
The correct role of banks in import/export transactions involving a letter of credit (L/C) is as follows: the importer's bank acts as the advising and/or confirming bank, while the exporter's bank acts as the issuing bank.
Step-by-step explanation:
In import/export transactions involving a letter of credit (L/C), the correct role of banks is as follows:
a. The importer's bank is the advising and/or confirming bank;
b. The exporter's bank is the issuing bank.
The advising bank is responsible for notifying the exporter of the L/C terms, while the confirming bank adds its confirmation to the L/C, making the payment more secure. The issuing bank, on the other hand, is the bank that opens the L/C on behalf of the importer.