Step 1: Understanding the Question:
The question asks to identify the word from the given options that was inserted into the Preamble of the Constitution by the 42nd Amendment Act, 1976.
Step 2: Key Concept:
The Preamble has been amended only once so far, by the 42nd Constitutional Amendment Act of 1976. This amendment made significant changes to the Constitution and is also known as the 'Mini-Constitution'.
Step 3: Detailed Explanation:
The 42nd Amendment added three new words to the Preamble:
1. Socialist
2. Secular
3. Integrity (added to the phrase 'unity and integrity of the Nation')
The words 'Sovereign', 'Democratic', and 'Fraternity' were part of the original Preamble.
From the given options, Socialism is the word that was added by the 42nd Amendment.
Step 4: Final Answer
The word 'Socialism' was added to the Preamble by the 42nd Amendment.