What Is an Open Account in the Context of International

What is an open account in the context of international trade?

A) An open account is an arrangement whereby the exporter automatically ships a specific quantity of a specific good to the importer at regular intervals.
B) An open account is an arrangement whereby the importer and the exporter agree on a time of payment after the importer receives the goods sold by the exporter.
C) An open account is an arrangement in which the importer and exporter agree to trade goods and net the amount owed rather than each paying the other for goods purchased.
D) An open account is an arrangement in which the importer agrees to pay the exporter for goods that have been shipped by the exporter but not received by the importer.