Explanation:

- Option 1: August Comte

- Known as a founder of sociology.

- Developed the theory of positivism.

- Did not specifically discuss the "theory of social solidarity law."

- Option 2: Marx

- Focused on class struggle and economics.

- Known for theories on capitalism and communism.

- Not related to the "theory of social solidarity law."

- Option 3: Duguit

- A French jurist credited with the "theory of social solidarity law" or "theory of various needs."

- His work focused on law as serving the needs of society and promoting social cooperation.

- Known for blending legal theory with sociological concepts.

- Correct Answer

- Option 4: Spencer

- Known for Social Darwinism and ideas on evolution in society.

- Did not specifically propound the "theory of social solidarity law."