Final answer:
FDIC insurance is the one that protects investors against the loss of cash and securities held at a brokerage firm.
Step-by-step explanation:
The protection that covers investors against the loss of cash and securities held at a brokerage firm is known as deposit insurance. Specifically, in the United States, the Federal Deposit Insurance Corporation (FDIC) is responsible for providing this deposit insurance. Any investor with a deposit at a bank that goes bankrupt is ensured to receive their money up to a certain amount (nowadays up to $250,000) because banks pay an insurance premium to the FDIC. This scheme was put into place to prevent bank runs and to restore confidence in the financial system, ensuring that in the case of bank failure, depositors would not lose their invested money.
Therefore, to answer the student's question, the following protects investors against the loss of cash and securities held at a brokerage firm: c) FDIC insurance. Options such as homeowner's insurance, renter's insurance, and health insurance do not provide this type of protection.