The proposition that language shapes the way individuals of a particular culture understand the world is known as:

The correct answer is A: Sapir-Whorf hypothesis.

The Sapir-Whorf hypothesis, also known as Whorfianism, is a linguistic theory that proposes that the structure of a language influences or determines the worldview or cognition of its speakers. Essentially, it suggests that the way people perceive, categorize, and think about the world is shaped by the grammatical and lexical categories available in their native language. For example, cultures with many words for snow might perceive snow differently from those with only one word.

• Option B: Leah and Harry hypothesis is incorrect. There is no widely recognized linguistic or psychological hypothesis by this name.
• Option C: Brown and Gilman hypothesis is incorrect. Roger Brown and Albert Gilman are notable for their work in sociolinguistics, particularly their research on pronouns of power and solidarity (e.g., the 'T/V distinction' in addressing others, like 'tu' vs. 'vous'). Their work focuses on social aspects of language use, not on how language structures a culture's understanding of the world in the broad sense of the Sapir-Whorf hypothesis.
• Option D: None of these is incorrect because the Sapir-Whorf hypothesis accurately describes the proposition.