Explanation:

- Option 1: Sorokin

- Pitrim Sorokin was a sociologist known for his works on social dynamics and cultural change, not primarily for defining cooperation through diads and triads.

- Option 2: M. Mead

- Margaret Mead was an anthropologist famous for her studies on culture and gender. Her work did not focus on diads and triads in the context of cooperation.

- Option 3: G. Simmel

- Georg Simmel was a sociologist who introduced concepts of diads (two-person groups) and triads (three-person groups) in social interactions.

- He explored how the dynamics of cooperation and conflict change with the addition of more members to a group.

- Option 4: W.J. Goode

- W.J. Goode was a sociologist best known for his work on family sociology. Diads and triads were not the focus of his studies.

Answer: Your choice, Option 3 - G. Simmel is correct.

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