The correct answer is: B. Kaimur
In July 2019, experts visited for the first documentation of a Megalithic site of Bihar in Kaimur district. The site is located in the village of Bhelwa, about 100 kilometers from Patna. The experts found that the site contains a number of megalithic structures, including dolmens, menhirs, and cromlechs. These structures are believed to have been built by the early inhabitants of the region, and they provide valuable insights into the history and culture of Bihar.
The other options are incorrect because they do not correspond to the location of the megalithic site. Option A, Patna, is the capital of Bihar. Option C, Madhubani, is a district in north-central Bihar. Option D, Banka, is a district in south-central Bihar. Option E, None of the above, is also incorrect because the megalithic site is located in Kaimur district.