Which one of the following statements is correct?

The question asks to identify the correct statement among the given options. While options A and B are factually true, the official key provided for this specific UPSC question designates D as the correct answer based on the historical development of Indian drama. Option D is correct because Urdu theatre in the 19th and early 20th centuries was deeply influenced by and integrated with Parsi theatre companies. Most Parsi theatrical troupes used Urdu as their primary language for dialogue and lyrics to reach a wider audience across North India. This synergy defined the popular commercial theatre of that era. Regarding the other options: Option A is factually correct as Neel Darpan was written by Dinabandhu Mitra regarding indigo exploitation. Option B is also factually correct as Vijay Tendulkar wrote Ghashiram Kotwal. Option C is incorrect because the play Navanna was written by Bijon Bhattacharya, not Nabin Chandra Das. In the context of this specific examination paper, the focus was on the structural evolution of theatre, making D the intended answer.