The largest number of Buddhists is found in

Maharashtra contains by far the largest Buddhist population in India. Textbooks note that nearly 80% of India’s Buddhists live in Maharashtra, identifying it as the primary concentration of the community nationally [1]. Census-based summaries likewise report that a substantial majority — roughly three quarters — of the country’s Buddhists reside in Maharashtra, making it the single state with the largest number of Buddhists compared with other states such as Karnataka, Uttar Pradesh or Bihar [2]. Given this clear concentration in Maharashtra in both textbook discussion and census-derived data, Maharashtra is the correct choice.

Sources

1. [1] Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 13: Cultural Setting > Fig. 13.16 Christian Population (2011) > p. 56
2. [2] https://pages.uoregon.edu/aweiss/indianfilmclass/Census%20of%20India%20religion%202011.pdf