Which part of the prokaryotic flagella is located intracellularly?

The basal body of the prokaryotic flagella is the component found intracellularly. It serves as the anchor that connects the flagellum to the cell membrane and is embedded within the cell's cytoplasmic membrane. This structure consists of a series of rings that enable the flagellum to rotate like a motor. The energy required for this rotation is derived from the proton motive force generated by the cell's metabolism, which is accessible to the basal body since it operates within the cell.

The filament and hook, in contrast, extend outward from the cell and are thus external structures. The filament is the long, whip-like part that propels the organism, while the hook is the curved connector between the filament and the basal body, providing flexibility for the flagellum's movement. The term "Digital body" does not refer to any recognized aspect of prokaryotic flagella and is not relevant in this context. Therefore, the correct answer encapsulates the function of the basal body as the crucial intracellular component of the flagellar structure.