Option D (Tarapur) is the correct answer. The context lists Tarapur (Maharashtra) as the first nuclear power project among the important nuclear power projects mentioned in the NCERT textbook. Tarapur was India's first atomic power station, established in Maharashtra. The other options - Kalpakkam (Tamil Nadu), Narora (Uttar Pradesh), and Rana Pratap Sagar (Rawatbhata near Kota, Rajasthan) - were established later as part of India's nuclear energy development program.