Explanation:

Let's identify the location of the operational nuclear power plant in Uttar Pradesh. \nOption A: Mathura is a city in Uttar Pradesh known for its religious significance and oil refinery. There is no nuclear energy plant located in Mathura. Therefore, Mathura is incorrect. \nOption B: Singrauli is a district in Uttar Pradesh (and Madhya Pradesh) known for its extensive coal reserves and numerous thermal power plants, earning it the title 'Energy Capital of India'. However, it does not host a nuclear energy plant. Therefore, Singrauli is incorrect. \nOption C: Narora, a town in the Bulandshahr district of Uttar Pradesh, is home to the Narora Atomic Power Station (NAPS). This is the only operational nuclear power plant in Uttar Pradesh, managed by the Nuclear Power Corporation of India Limited (NPCIL). Therefore, Narora is the correct location. \nOption D: Aligarh is a city in Uttar Pradesh, famous for Aligarh Muslim University and its lock industry. There is no nuclear energy plant located in Aligarh. Therefore, Aligarh is incorrect. \nHence, the Nuclear Energy Plant established in Uttar Pradesh is located in Narora.