Concept:The main obstacle in international trade is the difficulty of settling payments across nations with different monetary systems.
Explanation:Every country uses its own currency, such as the Naira, Dollar, or Pound.
A seller expects payment in the local currency, while the buyer operates with a different currency.
This creates the problem of exchanging money and dealing with fluctuating exchange rates.
Factors like distance, culture, and politics also affect trade, but these can be overcome more easily.
Currency differences are the greatest challenge because every transaction depends on a mutually acceptable medium of exchange.
Answer:D. Differences in currency.