Final answer:
The correct answer is International trade and customs. International trade requires a classification system for all products and services that will cross national borders.
Step-by-step explanation:
The correct answer is C) International trade and customs.
International trade involves the exchange of goods and services between countries. When products and services cross national borders, a classification system is needed to ensure proper regulation and documentation. This classification system helps in determining custom duties, tariffs, and other trade regulations.
For example, when importing or exporting goods, countries use the Harmonized System (HS) code to classify products based on their nature, use, and composition. This classification system assists in tracking trade statistics, enforcing trade policies, and facilitating international trade.