The national self-regulatory organization (SRO) for investment dealers is the Investment Industry Regulatory Organization of Canada (IIROC). An SRO is a non-governmental organization that sets and enforces rules and standards for its members in a specific industry or profession. IIROC is an SRO that oversees all investment dealers and their trading activity in Canada’s debt and equity markets. IIROC’s mandate is to protect investors and support healthy capital markets by ensuring high standards of conduct, competence, and compliance among its members and their representatives. Therefore, option D is correct regarding the national SRO for investment dealers. The other options are not correct or relevant to the question. Option A is false because there is no such organization as the National Securities Commission in Canada; rather, there are provincial and territorial securities regulators that form the Canadian Securities Administrators (CSA), which is a council of securities regulators that coordinates and harmonizes regulation for the Canadian capital markets. Option B is false because the Mutual Fund Dealers Association of Canada (MFDA) is not the national SRO for investment dealers; rather, it is the national SRO for mutual fund dealers and their representatives in Canada. Option C is false because the Canadian Securities Administrators (CSA) is not the national SRO for investment dealers; rather, it is a council of securities regulators that coordinates and harmonizes regulation for the Canadian capital markets. References: [IIROC - Home], [SROs | GetSmarterAboutMoney.ca], [CSA - Home]