The primary purpose of the World Trade Organization (WTO) is to promote free trade around the world. It serves as an international organization that regulates and facilitates international trade agreements, aims to reduce trade barriers, and fosters a stable trading environment among its member countries.
While the WTO does play a role in facilitating the international distribution of goods and may have some influence over tariffs and trade regulations, its main mission revolves around promoting free trade and resolving trade disputes. Therefore, the most accurate response from your list is promote free trade around the world.