Final answer:
The work often associated with the discussion of 'why be moral' in the context of society is 'The Social Contract' by Rousseau or 'The Republic' by Plato, which is not one of the listed options but aligns with the broader concept of the social contract.
Step-by-step explanation:
The classic work referenced when asking "why be moral" is often associated with the concept of the social contract. Philosophers have historically explored the relationship between ethics and politics, positing that living in a society requires individuals to embrace certain moral and political obligations.
The social contract theory, deeply rooted in the Enlightenment period, posits that individuals consent, either explicitly or tacitly, to surrender some of their freedoms and submit to the authority of the ruler or magistrate (the sovereign), in return for protection of their remaining rights.
The work that is often referenced in discussions about the social contract is not one of the options provided (A, B, C, or D). However, the most associated with the inquiry into moral conduct within the context of society would likely be Jean-Jacques Rousseau's 'The Social Contract,' or in Plato's dialogues that discuss the ideal state and justice, particularly 'The Republic'.