Which amendment made it mandatory for the President to give his assent to the Constitutional Amendment bills?

24th

The correct answer is Option 1 - 24th

The amendment that made it mandatory for the President of India to give his assent to Constitutional Amendment bills is the 24th Amendment.

This amendment came into effect on November 5th, 1971. It significantly increased the power of the Parliament to amend the Constitution, particularly regarding Fundamental Rights.