Concept:Chromatography separates the components of a mixture by carrying them at different speeds along a stationary medium.
Explanation:Black ink is a mixture of different coloured dyes and chemical compounds.
In paper chromatography, a small spot of black ink is placed on filter paper.
The paper is then dipped into a suitable solvent.
As the solvent rises, it carries the ink components along with it.
Each dye dissolves and moves at a different rate because the dyes have different solubilities and different attractions to the paper.
As a result, the single black spot separates into several distinct coloured spots on the paper.
This clearly shows that black ink contains more than one chemical compound, so it is a mixture.
In contrast, techniques such as crystallization, filtration, and sublimation cannot separate the coloured dyes from black ink in this visible manner.
Crystallization would not separate a mixture of soluble dyes, filtration would only remove undissolved solids, and sublimation only works for substances that change directly from solid to gas.
Thus, chromatography is the correct technique for demonstrating that black ink is a mixture.
Answer:B. Chromatography