Step 1: Understand the procedure for certain amendments.
Article 368 of the Constitution specifies that any amendment that seeks to change the "federal features" of the Constitution must be passed by a special majority in Parliament AND be ratified by the legislatures of at least half of the states.
Step 2: Identify federal features.
Federal features include the division of legislative powers, the representation of states in Parliament, and the provisions related to the Supreme Court and High Courts.
Step 3: Analyze the amendments.
The 1st, 42nd, and 73rd Amendments, while significant, did not all contain provisions that mandatorily required state ratification under Article 368.
The 73rd amendment, dealing with a state subject, did require ratification.
The 101\textsuperscript{st Amendment} introduced the Goods and Services Tax (GST).
This fundamentally altered the taxation powers of both the Centre and the States, which is a core federal feature.
It directly impacted the division of legislative powers in the Seventh Schedule.
Therefore, it mandatorily required ratification by the states, which it received.
Among the given options, the 101st Amendment is the clearest and most prominent example of an amendment requiring state ratification.