Concept:Demurrage is a penalty charged when a ship exceeds its agreed time at port.Explanation:When a vessel stays longer than the allowed number of days, it delays loading or unloading operations.This causes financial loss to the shipowner.To compensate, the port or shipowner charges the importer or charterer a fee.This fee is known as demurrage.It is not interest, tariff, or commission because those refer to different kinds of payments.Answer:C. demurrage