The reaction which can be used to prepare aryl halides is

Sandmeyer's reaction

The correct answer is Option (3) → Sandmeyer's reaction

Aryl halides are commonly prepared from diazonium salts using Sandmeyer reaction.

General reaction: Ar–N₂⁺ + CuX → Ar–X + N₂

Where X = Cl, Br, CN

This allows substitution of diazonium group with halogen.

OTHER OPTIONS

• Aldol reaction: Used for forming β-hydroxy aldehydes/ketones from aldehydes/ketones (carbon-carbon bond formation).
• Kolbe's reaction: (Kolbe-Schmitt) Used for preparing salicylic acid (introduces –COOH on phenol).
• Reimer-Tiemann reaction: Used for introducing –CHO group (formyl) on ortho position of phenol.