Final answer:
A multibank holding company is the type of entity that controls at least two commercial banks and is supervised by the Federal Reserve, while individual banks are regulated by the Office of the Comptroller of the Currency. The correct answer is option d.
Step-by-step explanation:
The entity that controls at least two commercial banks is known as a multibank holding company. These bank holding companies fall under the supervision of the Federal Reserve, which has been given a role to oversee financial institutions.
The Office of the Comptroller of the Currency, within the U.S. Department of the Treasury, on the other hand, is responsible for supervising individual banks, conducting on-site reviews, and monitoring banks' balance sheets for risk levels and positive net worth.
Bank holding companies can be complex entities that own not only multiple banks but also other types of businesses. Therefore, the correct answer to the student's question is that a multibank holding company controls at least two commercial banks. The regulation of these holding companies is crucial to ensure the stability of the financial system.