Which of the following securities allows for a limited number of investors and requires a minimum amount to participate?

Money market funds are open to a broad range of investors and do not impose strict limitations on the number of participants. They typically have low minimum investment requirements, making them accessible to the general public and suitable for those seeking a safe place to park cash with modest returns.

Preferred stock represents ownership in a company and can be issued to an unlimited number of investors without a minimum investment requirement. While it offers certain advantages over common stock, such as fixed dividends, it does not restrict participation based on investor count or initial investment size.

Open-end funds, which include mutual funds, allow for an unlimited number of investors and do not require a minimum investment that limits participation. These funds continuously issue and redeem shares as investors enter and exit, making them highly accessible investment options for the general public.