What group consists of fifteen developed countries representing 20% of the world's gross domestic product?

The correct choice refers to a group of developed countries known collectively as the European Economic Community (EEC), which originally aimed to promote economic integration among its members. The EEC played a crucial role in fostering collaboration and trade among its member nations, ultimately contributing to greater economic stability and growth within Europe. This group is significant in the context of the global economy, especially given that these nations collectively represent around 20% of the world's gross domestic product.

In contrast, other options like the Asian Development Bank focus primarily on regional development and financial assistance rather than forming a membership group based on economic integration. The World Trade Organization is concerned with regulating international trade and ensuring trade flows as smoothly and freely as possible, but it does not represent a specific group of developed countries. The North American Free Trade Agreement, while significant in facilitating trade between North America, does not encompass a broad spectrum of developed nations and is more regionally focused. Hence, the EEC aligns more closely with the context of developed countries constituting a notable portion of the world's GDP.