A hermetic refrigerant motor-compressor is characterized by which of the following?

A hermetic refrigerant motor-compressor is defined by its design, where the compressor and motor are integrated into a single sealed unit. This configuration provides several advantages, including enhanced efficiency and reduced risk of refrigerant leakage, as the entire assembly is hermetically sealed. This sealing protects the internal components from contaminants and ensures that the refrigerant remains contained within the system, which is critical for the effective operation of refrigeration and air conditioning systems.

In contrast, the options regarding an external shaft or motor suggest designs that are not hermetic, where components may be separate and exposed to the environment, making them susceptible to contamination and potential refrigerant loss. Additionally, stating that it operates without refrigerant does not align with the definition of a refrigerant motor-compressor, as its primary function is to compress refrigerant gas for cooling processes.