Explanation:

- Option 1: Nepal

- Dashain is indeed the grandest and most auspicious festival in Nepal.

- Celebrated by Nepalese people, it marks the victory of good over evil.

- It is similar to Durga Puja and Navratri, celebrated across other parts of South Asia.

- ?? Correct Answer

- Option 2: Bangladesh

- Dashain is not the grandest festival here.

- Bangladesh primarily celebrates Eid-ul-Fitr and Eid-ul-Adha as major festivals.

- Option 3: Bhutan

- Bhutanese celebrate festivals like Tshechu, but Dashain is not dominant here.

- Option 4: Sri Lanka

- The major festival in Sri Lanka is Vesak, a Buddhist celebration.

- Dashain is not recognized as a grand festival in Sri Lanka.