The Preamble of the Constitution was amended by the ______ Constitutional Amendment Act.

42nd

The correct answer is Option 4 - 42nd

The Preamble of the Constitution of India was amended by the 42nd Constitutional Amendment Act of 1976. This amendment is also sometimes referred to as the "Mini-Constitution" due to the extensive changes it introduced.

Changes to the Preamble:
Added Words: Three words were inserted into the Preamble: "Socialist," "Secular," and "Integrity of the Nation." This aimed to reflect India's commitment to those ideals.