The correct answer is R Venkataraman.

• The bill in which the eligibility age for the right to vote was reduced from 21 years to 18 years received assent from then-President Ramaswamy Venkataraman on 28 March 1989.
• Sixty-First Amendment Act, 1989:
  • ​Reduced the voting age from 21 years to 18 years for the Lok Sabha and state legislative assembly elections.
  • Article 326 of the Constitution of India deals with elections to the Houses and to the State Legislative Assemblies on the basis of universal adult suffrage.
  • The article before being amended by the 61st Amendment stated that any citizen of India who is 21 years or above, and who is not disqualified on any other grounds such as non-residence, crime, corrupt or illegal practices, or unsoundness of mind, is eligible to vote at an election.
  • The proposal to reduce the voting age to 18 years was brought about to increase the participation of the youth in the electoral process of the country.
  • The Constitution (Sixty-first Amendment) Act, 1988 was introduced in the Lok Sabha on 13th December 1988 by the then Water Resources Minister B. Shankaranand.
  • It was debated and passed by the lower house on 15th The Rajya Sabha passed the bill on 20th December.
  • As per law, more than half the state legislatures had to ratify the bill and this was duly obtained. Only five states, Jammu & Kashmir, Punjab, Nagaland, Tamil Nadu, and Tripura did not ratify.
  • The bill received the presidential assent on 28th March 1989 when the then President R Venkataraman assented it.
  • Thus, the act came into force on 28th March 1989 and from that day onwards, any citizen who is otherwise qualified could participate in the democratic processes in India from the age of 21 years.