Azo coupling reactions are a type of reaction that involves the formation of a new bond between two nitrogen atoms, resulting in the formation of an azo compound. These reactions are commonly used in organic synthesis to introduce azo functional groups into molecules.

The correct answer to the question is option 'C', which states that the azo products obtained in a coupling reaction involve both the N=N bond and electrophilic substitution reactions. Let's understand why this is the correct answer:

1. N=N Bond Formation:
- Azo coupling reactions involve the formation of a new N=N double bond between two nitrogen atoms.
- This bond formation occurs through the reaction of two aromatic diazonium salts (aromatic compounds containing a nitrogen-nitrogen double bond) in the presence of a coupling agent.
- The diazonium salt acts as the electrophile, and the coupling agent (such as phenol, aniline, or aromatic amines) acts as the nucleophile. The nucleophilic nitrogen atom attacks the electrophilic nitrogen atom, resulting in the formation of the N=N bond.

2. Electrophilic Substitution:
- Electrophilic substitution reactions involve the substitution of an atom or group in a molecule with an electrophile.
- In azo coupling reactions, the electrophilic substitution occurs in the aromatic ring of the coupling agent.
- The diazonium salt acts as the electrophile, and it substitutes the diazo group (-N2) with the coupling agent, leading to the formation of the azo compound.
- This substitution reaction is electrophilic because the diazonium salt is electron-deficient due to the presence of the positively charged nitrogen atom.

In summary, the correct answer option 'C' is justified because azo coupling reactions involve the formation of an N=N bond between two nitrogen atoms and the electrophilic substitution reaction in the aromatic ring of the coupling agent. These reactions are widely used in organic synthesis to introduce azo functional groups into molecules.