Step 1: Understanding the Question:
We need the amendment that was made as a reaction to one court judgement against Indira Gandhi.
Step 2: Think about what the amendment had to achieve.
The court had cancelled her election on the ground of malpractice. The easiest legal shield was to say that a court cannot examine the election of the Prime Minister at all.
Step 3: Look for that idea in the options.
Option (3) is exactly this idea. It also covers the President, the Vice President and the Speaker. This was the 39th Amendment.
Step 4: Test the other options.
Option (1) is about OBC reservation, which is unrelated. Option (2) is about the Emergency power, not about court cases. Option (4) is about the term of the legislatures, which was extended in steps of one year and not in response to this ruling.
Step 5: Conclude.
Only option (3) links directly to the Allahabad High Court case. It is also the change that the Supreme Court later struck down in part, which shows how closely it was tied to that dispute.
Final Answer:
The 39th Amendment protected the election of top officials from court challenge. Option (3) is correct.
\[ \boxed{\text{Option 3}} \]