“Chance process” (dense medium/coal washing): it is industrially used for which application among the following?

Introduction / Context:
The Chance process is a dense medium (suspension) separation historically used in coal preparation plants to separate coal from shale/stone based on density differences.

Concept / Approach:
Coal (lower density) floats in a magnetite-water (or sand-water) slurry while denser impurities sink. This improves coal quality by reducing ash and sulfur carriers. The method is distinct from ore concentration like magnetic separation for iron or flotation for sulfides.

Final Answer:
Cleaning of coal