Explanation:

- Option 1: Summer (Sumner) – He talked about in-group and out-group but didn’t emphasize the positive role of conflicts in group solidarity through resolving misunderstandings.

- Option 2: Dahrendorf – He is known for his work on conflict theory, but mainly in the context of authority and social change, not specifically about removing misunderstandings to increase group solidarity.

- Option 3: Weber – His focus was on bureaucracy, authority, and types of social action. He did not highlight conflicts as a way of enhancing group solidarity by resolving misunderstandings.

- Option 4: Simmel – He argued that conflicts can indeed strengthen group unity by clearing up misunderstandings, a process that often results in better cohesion. He viewed conflict as a form of socialization.

Correct Answer: Option 4 – Simmel.