Explanation:

- Option 1: Sitar

- The sitar is a plucked string instrument used in Indian classical music and is famous for its complex sound.

- Popular exponents of the sitar include artists like Ravi Shankar.

- Option 2: Mandolin

- The mandolin is a string instrument commonly used in bluegrass, classical, and folk music.

- It is not typically associated with traditional Indian classical music.

- Option 3: Veena

- The veena is a traditional Indian plucked string instrument.

- It is used in Carnatic music and has several variations like Saraswati veena.

- Option 4: Nadaswaram

- Correct Answer: Sheikh Chinna Moula was an exponent of the nadaswaram.

- The nadaswaram is a traditional South Indian wind instrument, commonly used in temple rituals and cultural events.

- It is considered auspicious and is a key part of classical Indian music performances.

Sheikh Chinna Moula is renowned for his mastery of the nadaswaram, helping to popularize the instrument on both national and international stages.