Concept:The correct phrasal verb is chosen based on the meaning of permanently stopping a business or operation.Explanation:"Close down" means to stop operating permanently, especially for a business or company."Close in" means to approach or surround someone or something."Close up" means to shut something, such as a building, or to become silent."Close on" is rarely used with this meaning.Therefore, the option that best matches the idea of ending operations is "closed down".Answer:D. closed down