Explanation:

- Option 1: G. Simmel

- Georg Simmel proposed that conflict is an integral part of social life.

- He believed that conflict can contribute to social integration and change, making it functional.

- Option 2: L. Coser

- Lewis Coser believed that social conflict can have a positive function.

- In his work, he expanded on Simmel's ideas, suggesting conflict can strengthen group ties and promote social unity.

- Option 3: Young and Mack

- These sociologists did not focus directly on the functionality of social conflict in their work.

- Their perspective wasn't specifically about conflict being functional.

- Option 4: Both a and b

- Both Simmel and Coser believed in the functional aspects of social conflict.

Correct Answer: Option 4 - Both a and b