In a multi stage, reciprocating compressor the highest pressure stages may be:

In a multi-stage reciprocating compressor, the highest pressure stages are typically single acting. Single-acting refers to the design of the compressor cylinder where the compression process occurs on only one side of the piston during each stroke. This design is particularly advantageous in high-pressure applications because it allows for a more efficient compression process as the compressor can maintain consistent output and pressure.

Single-acting cylinders also tend to have a simpler design with fewer moving parts compared to double-acting cylinders, which operate on both sides of the piston. In high-pressure stages, reliability and effectiveness are crucial, making the single acting configuration a preferred choice.

The other options, such as remote control, poppet valve regulation, or double lobe configurations, address different aspects or designs of compressor function but do not specifically pertain to the nature of the highest pressure stages in terms of their operation and efficiency in a multi-stage setup.