Final answer:
Plato (option A) is the author referenced regarding 'why be moral?' and it is John Locke who argued that all people are born free with government existing by consent, contrasting Thomas Hobbes' belief in the necessity of a strong government.
Step-by-step explanation:
The author of the classic work frequently referenced in discussions of the question "why be moral?" is Plato. Plato, in his dialogues, especially in works like the Republic, explores the nature of justice and morality, prompting considerations of why individuals should act virtuously even in the absence of external rewards or recognition. This question of moral conduct and its intrinsic worth is a central theme in Socratic and Platonic philosophy.
Concerning the philosopher who argued that all people are born free in a state of nature and that the government should exist only by their consent, the correct answer is John Locke. This principle is fundamentally different from the views of Thomas Hobbes, who believed in a strong authoritative government to restrain natural selfish desires which would be rampant in the state of nature.
Aristotle, another key figure in philosophy, emphasized that humans are inherently social beings, and our interactions within society play a crucial role in moral development, as outlined in his work, Nicomachean Ethics. In contrast, Hobbes's views in Leviathan suggest that a powerful government is necessary to prevent the chaos that would ensue from our natural inclination towards self-interest.