ANS:B - leaching.

Leaching is a separation process used to extract soluble components or compounds from a solid material by using a liquid solvent. It is commonly employed in various industries for extracting valuable metals from ores, removing contaminants from soil or solid waste, and extracting flavor, color, or active compounds from natural products like herbs, spices, and coffee. Here's how leaching typically works:

1. Solid-Liquid Contact: The solid material containing the desired soluble components is placed in contact with a liquid solvent, typically in a vessel or tank. The solvent can be water or any other suitable liquid that can selectively dissolve the desired compounds.
2. Mass Transfer: The soluble components in the solid material dissolve into the liquid solvent, forming a solution. This process occurs due to the contact between the solid surface and the solvent, as well as the diffusion of the solute molecules from the solid phase into the liquid phase.
3. Separation: After sufficient contact time between the solid and liquid phases, the solution is separated from the solid material. This can be achieved through methods such as filtration, settling, or centrifugation, depending on the nature of the solid material and the desired purity of the extracted solution.
4. Recovery: The extracted solution, now enriched with the desired soluble components, is further processed to recover the target compounds. This may involve additional purification steps such as evaporation, crystallization, or solvent extraction to isolate and concentrate the desired compounds from the solution.

Leaching can be conducted under various conditions, including atmospheric pressure or elevated pressure and temperature, depending on the specific requirements of the process. Factors such as the choice of solvent, particle size of the solid material, contact time, temperature, and agitation level can all influence the efficiency and effectiveness of the leaching process. Overall, leaching is a versatile and widely used technique for extracting soluble components from solid materials, offering advantages such as simplicity, scalability, and selectivity for specific target compounds.