What is mandatory for becoming a FIFA member association?

To become a FIFA member association, it is indeed mandatory for the organization to be responsible for all football-related activities within the country. This responsibility includes overseeing the organization of national competitions, the development of the sport at all levels, and maintaining the regulations established by FIFA. This requirement ensures that FIFA can maintain a standard for governance and structure across all member associations, which is crucial for the integrity and organization of international football.

While operating in a democratic country, being a member of a confederation, and having football as the main sport can contribute to a nation's participation in FIFA, they are not mandatory for membership. The central focus for FIFA is on the organizational role of the member association in governing football, which is what makes option A the correct answer. This structure allows FIFA to promote unity within the sport while providing a framework for competition and development on a global scale.