The correct answer is B. Kaimur.
The Kaimur series rocks are found in the Kaimur district of Bihar. The Kaimur district is located in the southern part of the state, and is bordered by the districts of Rohtas to the north, Buxar to the east, Aurangabad to the south, and Jharkhand to the west. The district has a total area of 3,268 square kilometers, and a population of over 2.5 million people. The headquarters of the district is the town of Arrah.
The Kaimur series rocks are a group of sedimentary rocks that were formed during the Jurassic period. The rocks are composed of sandstone, shale, and limestone. The Kaimur series rocks are important because they contain a variety of fossils, including dinosaurs, fish, and plants. The rocks are also used as a source of building materials.
The other options are incorrect because they are not districts in Bihar where the Kaimur series rocks are found. Option A, Bhojpur, is a district in the central part of Bihar. Option C, Buxar, is a district in the eastern part of Bihar. Option D, Aurangabad, is a district in the southern part of Bihar.