- Statement A is incorrect: Dr. Manmohan Singh served two consecutive terms as Prime Minister (2004-2009 and 2009-2014), thus completing a full five-year term and returning to power. However, he was not the first Indian Prime Minister to achieve this. Jawaharlal Nehru also completed full five-year terms (e.g., 1952-1957, 1957-1962) and returned to power. - Statement B is correct: Dr. Manmohan Singh served as the Union Minister of Finance under Prime Minister P.V. Narasimha Rao from 1991 to 1996, during which he was instrumental in India's economic reforms. - Statement C is correct: Before becoming Finance Minister, he served as the Governor of the Reserve Bank of India (1982-1985) and subsequently as the Deputy Chairman of the Planning Commission (1985-1987). - Statement D is correct: He was indeed the Leader of the Opposition in the Rajya Sabha from 1998 to 2004.