Explanation:

- Sublimation: Used to purify organic compounds that can transition directly from solid to gas. It's effective for compounds that sublimate without decomposing.

- Crystallisation: Utilized for purifying solid organic compounds. It involves dissolving the compound in a solvent and then allowing it to form crystals.

- Distillation: Ideal for separating mixtures based on different boiling points. It's commonly used to purify liquids.

- Sedimentation: Typically used for separating suspended particles from liquids. It's not suitable for purifying organic compounds.

Correct Answer: Option 4, Sedimentation