Final answer:
Watercolor is the medium that exists between drawing and painting, as it offers the fluidity of ink while also allowing for brush control, making it suitable for both fine lines and broader color applications.
Step-by-step explanation:
The medium that exists somewhere between drawing and painting, similarly to ink which can be drawn with a pen or painted with a brush, is watercolor. Watercolor is a wet medium just like ink, and it is also characterized by its ability to be applied in both thin washes using a brush, creating a variety of transparent layers, or in more concentrated forms to create stronger, more opaque colors and lines. This versatility allows watercolor to straddle the line between drawing and painting, offering a broad range of artistic possibilities.
While charcoal and graphite are primarily considered dry drawing media, and pastel offers effects akin to painting due to its ability to blend, none quite match the unique properties of watercolor that allow it both to flow with liquid precision and also offer brushstroke control.
Therefore, the answer to the question is c) Watercolor.