ANS:D - Removing nicotine from its water solution by kerosene.

The operation that does not involve leaching is:

• Removing nicotine from its water solution by kerosene.

Leaching typically involves the extraction of a soluble substance from a solid material by using a liquid solvent. In the given options:

• Dissolving gold from ores involves leaching, as it typically employs a chemical solution (such as cyanide) to extract gold from the ore.
• Dissolving pharmaceutical products from bark or roots can involve leaching, as it often entails extracting medicinal compounds using solvents.
• Dissolving sugar from the cells of the beet involves leaching, as it requires using water to extract sugar from the beet cells.

However, removing nicotine from its water solution by kerosene does not involve leaching. Instead, it likely involves liquid-liquid extraction or another separation process.