The correct answer is (a) Sixty third Amendment.
The Sixty-third Amendment to the Constitution of India, enacted in 1989, reduced the voting age from 21 to 18 years. The amendment was passed by the 9th Lok Sabha and ratified by the requisite number of state legislatures. The amendment came into effect on 25 April 1989.
The amendment was brought about in response to the demand for lowering the voting age from various quarters. The argument in favor of lowering the voting age was that it would give a voice to the youth of the country and make them feel more involved in the democratic process. The amendment was also seen as a way to increase the voter turnout in elections.
The amendment was not without its critics. Some argued that lowering the voting age would lead to an increase in the number of illiterate voters and that this would not be in the best interests of democracy. Others argued that the amendment would not have a significant impact on the voter turnout.
Despite the criticism, the Sixty-third Amendment has been seen as a positive step towards making the Indian democracy more inclusive. The amendment has given a voice to the youth of the country and has made them feel more involved in the democratic process. The amendment has also led to an increase in the voter turnout in elections.
The other options are incorrect because they are not the amendments that reduced the voting age from 21 years to 18 years.