The correct answer is: B. Kaimur
The Vindhyan group of rocks are found in the Kaimur district of Bihar. The Vindhyan Supergroup is a sedimentary rock sequence that is found in the central and eastern Indian subcontinent. It is the oldest rock formation in India and is dated to the Proterozoic Era. The Vindhyan Supergroup is divided into three groups: the Lower Vindhyan, the Middle Vindhyan, and the Upper Vindhyan. The Lower Vindhyan is the oldest group and is made up of sandstone, shale, and limestone. The Middle Vindhyan is made up of sandstone, shale, and conglomerate. The Upper Vindhyan is made up of sandstone, shale, and limestone. The Vindhyan Supergroup is important because it is the source of many of India’s coal deposits. It is also important because it is a record of the Earth’s history during the Proterozoic Era.
The other options are incorrect because they are not districts in Bihar where the Vindhyan group of rocks are found. Option A, Gaya, is a district in Bihar, but the Vindhyan group of rocks are not found there. Option C, Buxar, is a district in Bihar, but the Vindhyan group of rocks are not found there. Option D, Banka, is a district in Bihar, but the Vindhyan group of rocks are not found there.