What process swells the emulsion to allow chemical penetration?

The correct answer is based on the understanding of how photographic emulsions interact with chemicals during the development process. Wetting refers to the process by which the surface tension of water is reduced, enabling the developer solution to penetrate and spread across the emulsion layer of the film or photographic paper more effectively. This increased penetration is critical because it allows the developing chemicals to interact thoroughly with the silver halide crystals in the emulsion, facilitating the development of the latent image.

The other processes mentioned serve different roles within the photographic workflow. Developing is the act of chemically reducing the exposed silver halide to metallic silver, which forms the visible image. Fixing involves removing unexposed silver halides, making the image stable and no longer sensitive to light. Rinsing is simply the process of washing away excess chemicals and is typically done after fixing to stop any chemical reaction that might still be occurring in the emulsion. Each of these processes is essential, but wetting specifically addresses the initial interaction between the emulsion and the chemicals used in development.