Step 1: Understanding the Concept:
The question asks to identify the specific policy rate used by the RBI for long-term lending to commercial banks.
Step 2: Detailed Explanation:
Let's define the given rates:
\begin{itemize}
\item Repo Rate: The rate at which the RBI lends money to commercial banks for their short-term needs, against the security of government bonds.
\item Bank Rate: The rate at which the RBI lends money to commercial banks for their long-term needs, without any collateral. It is also the rate at which the RBI rediscounts bills of exchange.
\item Reverse Repo Rate: The rate at which the RBI borrows money from commercial banks.
\item Margin Requirement: This is a qualitative tool of credit control, not an interest rate. It refers to the difference between the market value of a security and the loan amount granted against it.
\end{itemize}
The question specifically mentions "long-term requirements," which directly corresponds to the definition of the Bank Rate.
Step 3: Final Answer:
The rate for long-term borrowing by commercial banks from the RBI is the Bank Rate. Therefore, option (B) is correct.