The correct answer is C. Hundi.
A bill of exchange is a written order from one party (the drawer) to another party (the drawee) to pay a specified amount of money to a third party (the payee). A letter of credit is a document issued by a bank that guarantees payment to a seller on behalf of a buyer. A telegraphic transfer is a method of transferring money electronically between banks. A hundi is an informal bill of exchange used in India and Pakistan.
Hundi is not a method of foreign exchange because it is not a formal instrument. It is an informal bill of exchange that is used in India and Pakistan. It is not accepted by banks and other financial institutions as a method of payment.