Concept: National unity is strengthened by actions that bring different ethnic groups together.
Explanation:• Formal education helps, but it does not directly unite families from different ethnic groups.
• Good environmental practices focus on caring for the environment, not on unity among people.
• Opinion leaders can influence people, but their effect on unity may be limited.
• Inter-ethnic marriages create direct family and social ties between different ethnic groups.
• This makes inter-ethnic marriages the most effective way to promote unity among Ghanaians.
Answer: C. inter-ethnic marriages