Step 1: Recall how education became a right.
Education started as a Directive Principle. Later the Supreme Court linked it to the right to life, and then an amendment made it a clear fundamental right.
Step 2: Identify the amendment.
The 86th Constitutional Amendment Act, 2002 made this change.
Step 3: Know what it added.
It inserted Article 21A, giving free and compulsory education to children aged 6 to 14, and added a matching fundamental duty under Article 51A(k).
Step 4: Rule out the others.
The 42nd added fundamental duties, the 44th changed emergency rules, and the 73rd brought in Panchayati Raj.
Answer: 86th Constitutional Amendment Act (Option 4).