Which of the following constitute non-tariff barriers to trade?

Explanation

Non-tariff barriers are restraints on international trade which are not so obvious as simple duties or tariffs. Complex procedures can slow things down, reducing the incentive to export to that country resulting in protected domestic business; subsidies to one's own producers make it more difficult for foreign firms to compete - again creating a barrier to trade.

Increased import duties would be a form of tariff (potentially in breach of GATT / WTO agree-ments); reduced import duties would free up / encourage trade.