Which of the following refrigerants is identified as R-717?

R-717 is the designation for ammonia, a refrigerant that is commonly used in industrial applications due to its high efficiency and low environmental impact. Ammonia is favored in many large-scale cooling operations, such as in food processing and refrigeration, because it has excellent thermodynamic properties that allow for effective heat transfer. Additionally, it has a low global warming potential and does not deplete the ozone layer, making it an environmentally friendly option when handled properly. In contrast, the other options—Freon, propane, and butane—refer to different types of refrigerants that are less commonly used in industrial settings compared to ammonia.