Which of the following is NOT considered a non-tariff barrier (NTB)?

Non-tariff barriers (NTBs) are regulatory and policy measures, other than tariffs, that countries use to control the amount of trade across their borders. These can include a wide variety of restrictions and regulations applied to imports and exports.

In this context, currency exchange rates are not categorized as a non-tariff barrier because they pertain to the value of currency and the conversion of money between countries. While currency exchange rates can influence trade by affecting pricing, they do not directly restrict the flow of goods and services; rather, they reflect the economic conditions and relative value of different currencies in the global market.

On the other hand, quotas, import licenses, and product labeling are all specific regulatory measures that impose restrictions on the quantity of goods entering a market, require permission for imports, or dictate how products should be presented to consumers. Each of these can affect trade flows and market access in a manner typical of NTBs.