Explanation:

- Option 1: Karl Marx

- Marx described religion as "the opium of the people," suggesting it offers comfort in a harsh world.

- The "heart of the heartless" phrase captures its role in providing solace despite systemic issues.

- ?? Correct answer: This is attributed to Karl Marx.

- Option 2: Max Weber

- Weber focused on religion’s role in shaping economic life, notably in "The Protestant Ethic and the Spirit of Capitalism."

- Option 3: Emile Durkheim

- Durkheim emphasized religion’s function in maintaining social cohesion and collective conscience.

- Option 4: Robert K. Merton

- Merton is known for theories on social structure and anomie, not predominantly focused on religion.