Step 1: Understanding the Question.
The question asks which of the four listed bodies does not have its origin written into the Constitution of India.
Step 2: Key Fact.
Three of the bodies are constitutional bodies, meaning the Constitution itself creates them and lays down their powers: the Election Commission under Article 324, the Public Service Commissions under Articles 315 to 323, and the Finance Commission under Article 280.
Step 3: Detailed Explanation.
The Planning Commission does not appear in any Article of the Constitution. It was set up in 1950 by a simple resolution of the Cabinet, which makes it an extra-constitutional or executive body, not a constitutional one.
Because it was created by an executive order and not by the Constitution, it could later be dissolved and replaced without a constitutional amendment, which is exactly what happened when it was replaced by the NITI Aayog in 2015.
The other three bodies, being rooted in specific Articles, cannot be removed as easily since doing so would require a constitutional amendment.
Step 4: Final Answer.
The body not provided for in the Constitution is the Planning Commission, so option (B) is correct.