The theory of "natural rights" refers to the belief that individuals possess certain inherent and inalienable rights. Option 1, Hobbes, did not propound this theory. Hobbes believed in a social contract where individuals willingly give up their rights to a governing authority in exchange for protection and stability. Option 3, Bentham, is also incorrect as he believed in utilitarianism, which emphasizes the greatest good for the greatest number of people, rather than individual rights. Option 4, Marx, is known for his theory of communism and did not focus on natural rights. Therefore, option 2, Locke, is the correct answer. John Locke, an English philosopher, argued that individuals have natural rights to life, liberty, and property, and that these rights should be protected by government. Locke`s ideas greatly influenced the development of modern democratic governments and the concept of human rights.