Which of the following factors necessitates the adoption of federalism in a state?

The factor that necessitates the adoption of federalism in a state is "Fear of one ethnic group dominating the others". Federalism allows for the distribution of power and resources among various levels of government, which can help prevent one ethnic group from dominating the others. By sharing power and resources, each group can have a say in how the government is run and how resources are allocated. This can promote greater stability and unity in a state by ensuring that no one group is unfairly favored over others. The adoption of a written constitution, the availability of natural resources, or the encouragement of secession may be relevant to federalism in certain contexts, but they do not necessarily necessitate the adoption of federalism in a state.