Solution:Concept- Anthracene is a polycyclic aromatic hydrocarbon whose molecular formula is . It consists of three fused benzene rings. It is a crystalline and flammable solid and has a very faint aromatic odour. It is present in abundance.
Now, various separation methods are explained as-
Filtration is the process by which solid particles are separated from a liquid.The liquid that separates from the solid is called the filtrate.The filtration process takes place using a separatory funnel.
Crystallisation is the process by which a chemical changes from a liquid to a solid crystalline form.
Distillation is the process of separating liquid-liquid or solid-liquid mixtures through selective boiling and condensation processes.
When a solid substance directly changes its state from solid to gaseous on heating without going through the liquid phase, then this process is known as sublimation.
The substance that can undergo sublimation is called sublimate.
So basically out of all these methods, the only method that anthracene is purified by is the sublimation method.
Anthracene is solid and volatile in nature.
Due to its volatile nature, it easily transforms from solid to gaseous form.
Hence, the correct answer is 4.