Concept:Urbanization in colonial Nigeria created new social groupings and avenues for collective action, especially through labor and politics.
Explanation:Urban centers drew diverse Nigerian workers into factories, docks, and government offices.
Living and working together exposed shared hardships such as low wages and poor conditions.
This encouraged the formation of labor unions and strike movements.
Those unions later supported political activism and nationalist demands for better representation and self-rule.
The other options are incorrect because there was no complete assimilation into British culture, traditional chieftaincy institutions did not simply decline as a direct urban result, and urbanization did not erase ethnic or regional differences.
Answer:C. The growth of labor unions and political activism.