(A) SEBI
Portfolio Management Services (PMS) could be offered only by intermediaries having specific approval of SEBI for PMS.
SEBI (Securities and Exchange Board of India) is the apex regulatory body for the securities market in India. It grants specific approval to intermediaries for offering Portfolio Management Services. This is a standard regulatory fact tested in finance/capital markets MCQs. The source passages focus on market mechanics, but SEBI's role as the approving authority for PMS is a well-established SEBI regulation fact — none of the other options (RBI, NSDL, NSE) have authority to approve PMS.