India's first nuclear research reactor Apsara was established in which year?

The correct answer is Option B — 1956. Apsara was India's first nuclear research reactor established in August 1956 at BARC (Bhabha Atomic Research Centre) Trombay Mumbai. It was a swimming pool type reactor using enriched uranium fuel and ordinary water as moderator. Prime Minister Jawaharlal Nehru named it Apsara. Option A is incorrect: 1947 is the year of India's independence. There was no nuclear reactor in India at that time. The nuclear programme was just beginning under Homi Bhabha. Option C is incorrect: 1972 is the year Purnima-1 reactor was established at BARC which used plutonium oxide as fuel. It was India's first fast neutron reactor not the first nuclear reactor. Option D is incorrect: 1985 is the year Dhruva reactor was established at BARC. It is India's largest research reactor with 100 MW thermal power.