p-Hydroxyazobenzene is also known as

The correct answer is option 3. Orange dye.

p-Hydroxyazobenzene is an orange-colored azo dye that is commonly used in various applications, including coloring textiles, plastics, and cosmetics. It is synthesized by coupling benzene diazonium chloride with phenol under alkaline conditions. The orange color of p-hydroxyazobenzene arises from the extended conjugation of the azo group with the benzene rings.