The correct answer is A. Regulation Q.
Regulation Q was a regulation of the Federal Reserve System that limited the interest rates that banks could pay on deposits. This regulation was in effect from 1933 to 1986. Money market funds were created in the 1970s as a way to circumvent Regulation Q. Money market funds are mutual funds that invest in short-term, low-risk securities, such as Treasury bills and commercial paper. They offer higher interest rates than traditional bank accounts, and they are not subject to Regulation Q.
Regulation M is a regulation of the Federal Reserve System that governs the extension of credit by banks to their customers. Regulation D is a regulation of the Federal Reserve System that governs the reserve requirements of banks. Regulation B is a regulation of the Federal Reserve System that prohibits discrimination in lending.