Step 1: Understand the role of monetary policy.
Monetary policy involves controlling money supply and interest rates to achieve economic stability, a function typically managed by a central banking authority.
Step 2: Identify the responsible body.
In India, the Reserve Bank of India (RBI) is the central bank responsible for formulating and implementing monetary policy.
Step 3: Eliminate distractors.
(B) Ministry of Finance frames fiscal policy, not monetary policy.
(C) and (D) Ministry of Commerce and related combinations focus on trade, not monetary policy.
(E) Planning Commission deals with economic planning, not monetary policy.
Therefore: The correct answer is (A). \[
\boxed{\text{A}}
\]