Which system allows for the use of multiple refrigerants?

The option involving a compound multistage compressor system is the correct answer because this type of system is specifically designed to handle different refrigerants at various stages of the compression process. In such systems, each stage can operate using different refrigerants based on temperature and pressure requirements, which enhances efficiency and performance.

This capability is particularly advantageous in applications that require precise temperature control or when operating with refrigerants that have varying characteristics. Additionally, multistage systems can optimize cooling performance and energy efficiency by adapting to the specific properties of each refrigerant at different stages, thereby improving the overall functionality of the refrigeration system.

While other systems, like the single-stage compressor system or those using scroll and reciprocating mechanisms, primarily focus on a single refrigerant type for their operation, they do not offer the flexibility and adaptation that a compound multistage compressor system provides for utilizing multiple refrigerants.