Concept:Cowries were a form of commodity money used as a medium of exchange before legal tender and credit instruments existed.Explanation:In early trade, valuable objects such as cowrie shells were widely accepted for buying and selling goods.They served as a practical medium of exchange and helped reduce the difficulties of barter, like the double coincidence of wants.Currency notes, cheques, and bank drafts are modern legal tender or credit instruments, so they only came into use later.Answer:The correct option is B. Cowries.