Option 3: (B), (A), (D), (C) -> The logical arrangement starts with (B) explaining why price control is needed - a fall in price below a certain level is undesirable. This establishes the rationale. Next, (A) introduces the government's response by setting floors or minimum prices. Then (D) elaborates on this action by stating the government imposes a lower limit on price. Finally, (C) provides the technical definition, naming this mechanism as a 'price floor'. This sequence follows a natural progression: problem identification → government action → implementation method → terminology definition. -> correct