The correct answer is D. WTO
Step-by-step explanation
WTO stands for World Trade Organization which is an organization that deals with international trade and replaced the General Agreement on Tariffs and Trade. The WTO role is to regulate the trade of service goods and others between the countries including trade agreements and resolution of disputes. Considering tariffs are taxes paid for importation or exportation and thus, tariffs are part of the trade, the World Trade Organization is the institution in charge to provide a framework for the resolution of a dispute on tariffs between two countries.