Explanation:

- Ustad Bismillah Khan was a renowned Indian musician.

- He is celebrated for popularizing the Shehnai, a traditional Indian wind instrument.

- The Shehnai has a distinct sound and is often played at weddings and auspicious occasions in India.

- Option 2, the Sitar, is a stringed instrument associated with maestros like Ravi Shankar.

- Option 3, the Guitar, is widely used in various music genres but not Bismillah Khan’s instrument.

- Option 4, the Santoor, is a stringed instrument associated with artists like Shivkumar Sharma.

The correct answer is Option 1: Shehnai.

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