Human rights are most likely categorized as an external social factor.

Human rights (A): Human rights issues pertain to the broader societal impacts and obligations of companies towards external stakeholders, including communities and individuals affected by the company's operations. These are external social factors because they involve the company’s interaction with the society at large.

Product liability (B): Product liability is typically considered an external factor but is more related to legal and regulatory compliance rather than social factors.

Working conditions (C): Working conditions are internal social factors as they pertain to the company's treatment of its employees and the internal work environment.