To determine the factors contributing to regionalism in India, we must analyze the role of various diversities as potential roots:
- Diversity of languages: India is home to a myriad of languages, with different regions identifying strongly with their respective linguistic heritages. This linguistic diversity fosters regional identities and distinctions, contributing to regionalism. Thus, option (A) is relevant.
- Diversity of cultures: India's rich and varied cultural traditions across different regions act as a source of regional pride and identity. These cultural variations play a significant role in strengthening regionalism as distinct cultural practices and festivals are celebrated. Thus, option (B) is pertinent.
- Diversity of castes: While caste diversity exists, it is more intertwined with social hierarchies and does not directly contribute to regional identity in the same way as language or culture. Therefore, option (C) is less relevant in this context.
- Diversity of religions: Different regions in India often have predominant religious communities, which can impact regional identity and lead to regionalism. This is a valid point, making option (D) applicable.
Considering these points, the factors most contributing to regionalism in India are the diversity of languages, cultures, and religions.
Therefore, the correct answer is: (A), (B) and (D) only.