The correct answer is (a) Dr. Rajendra Prasad.
Dr. Rajendra Prasad was the first President of India. He was elected unopposed in 1950. He was re-elected unopposed in 1957. He served as President of India for two terms, from 1950 to 1962.
V.V. Giri was the fourth President of India. He was elected in 1969. He defeated the incumbent President, Zakir Hussain, by a narrow margin.
Neelam Sanjeeva Reddy was the sixth President of India. He was elected in 1977. He defeated the incumbent President, Fakhruddin Ali Ahmed, by a comfortable margin.
Pranab Mukherjee was the 13th President of India. He was elected in 2012. He defeated the incumbent Vice President, Hamid Ansari, by a comfortable margin.
Dr. Rajendra Prasad was the only President of India who was elected unopposed. He was a highly respected leader who played a key role in the Indian independence movement. He was also a strong advocate for secularism and democracy.