Explanation:

- Option 1: Social Facts

- Social facts refer to societal norms, values, structures, and customs that influence individual behaviors.

- Durkheim studied social facts to understand their external and coercive effects on people.

- Option 2: Religion

- Durkheim examined the role of religion in society, focusing on the collective aspects and its unifying function.

- He viewed religion as a social phenomenon contributing to social cohesion.

- Option 3: Suicide

- Durkheim used concomitant variation in his study of suicide to examine how different social variables correlate with suicide rates.

- He discovered patterns linking social integration and regulation with suicide types.

- Option 4: Division of Labour

- This concept explains how labor specialization contributes to social solidarity.

- Durkheim emphasized the transition from mechanical to organic solidarity through labor division.