What is the primary function of an investment bank?

The primary function of an investment bank is to underwrite new debt and equity securities for corporations. This role is critical in the financial market, as investment banks facilitate the process through which companies raise capital by issuing stocks or bonds. They assess the company's financial needs, perform valuations, and help structure the offerings. Additionally, investment banks often serve as intermediaries, ensuring that the securities meet regulatory requirements and are marketed effectively to potential investors.

While personal banking services, managing retirement accounts, and providing loans to small businesses are important functions in the broader banking landscape, they are primarily associated with commercial banks or other financial institutions, rather than investment banks. The core mission of an investment bank revolves around capital markets, mergers and acquisitions, advisory services, and complex financial transactions. Thus, the response indicating the underwriting of securities aligns perfectly with the essential activities performed by investment banks.