What does the Glass-Steagall Act primarily restrict?

The Glass-Steagall Act primarily restricts commercial national banks from most investment banking activities, which was a critical aspect of its design. Enacted in 1933 in the wake of the Great Depression, the act aimed to separate commercial banking from investment banking to minimize the risk of financial speculation and conflicts of interest.

By limiting the activities of commercial banks, the act intended to protect depositors' savings by ensuring that the banks engaged primarily in traditional deposit-taking and loan-making functions, rather than in riskier investment banking activities that could jeopardize the safety of depositors’ funds. This separation was believed to reduce systemic risks in the financial system by ensuring a clear distinction between banking and securities operations.

The other options, while they may touch on aspects of banking and investment operations, do not reflect the primary intent and enforcement focus of the Glass-Steagall Act as accurately as the correct answer.