To answer this question, you need to have knowledge about the individuals who played a significant role in India's first nuclear explosion at the Pokhran range in 1974.
Option A) Raja Ramanna - This option is correct. Raja Ramanna was a prominent Indian physicist and a key figure in India's nuclear program. He played a crucial role in organizing and overseeing the successful "Smiling Buddha" nuclear test conducted on May 18, 1974, at the Pokhran range in Rajasthan. Therefore, Raja Ramanna was instrumental in staging India's first nuclear explosion.
Option B) Dr. APJ Abdul Kalam - This option is incorrect. Although Dr. APJ Abdul Kalam was an eminent scientist and a significant contributor to India's missile program, he was not directly involved in the Pokhran nuclear test in 1974.
Option C) Satish Dhavan - This option is incorrect. Satish Dhavan was an accomplished Indian scientist and the former Chairman of the Indian Space Research Organization (ISRO). While he made significant contributions to India's space program, he was not involved in the Pokhran nuclear test in 1974.
Option D) Homi Bhabha - This option is incorrect. Homi Bhabha was a renowned Indian physicist and the founding director of the Tata Institute of Fundamental Research (TIFR). Although Bhabha played a crucial role in initiating India's nuclear program, he passed away in 1966, years before the Pokhran nuclear test took place in 1974.
The correct answer is A) Raja Ramanna. He was instrumental in staging India's first nuclear explosion at the Pokhran range in 1974.