Concept:A major challenge of Nigeria’s federal system is the unequal composition and size of its component states.
Explanation:Nigeria moved from a few large regions to many smaller states, but these states are not equal in size, population, or resources.
This imbalance makes fair representation, resource sharing, and balanced development very difficult.
It also creates rivalry among states and raises the fear of domination by larger units.
Therefore, the major problem indicated in the options is the imbalance in the structure and sizes of the units of the federation.
Answer:A. imbalance in the structure and sizes of units of federation.