Which organization works to promote fair trade practices among countries?

The World Trade Organization (WTO) is the organization that works to promote fair trade practices among countries. It aims to create a platform for negotiating trade agreements, resolving trade disputes, and ensuring that trade flows as smoothly, predictably, and freely as possible. Part of its mission includes establishing trade rules that help facilitate fair competition among member nations, contributing to a more equitable trading system.

The other organizations listed have distinct roles that do not primarily focus on trade fairness. The World Health Organization (WHO) is concerned with global public health issues, the Food and Agriculture Organization (FAO) focuses on defeating hunger and improving nutrition and food security, and the World Bank aims to reduce poverty by providing financial and technical assistance to developing countries, which may include but is not limited to trade issues. Thus, the WTO's specific function in promoting fair trade practices distinguishes it as the correct answer.