Which of the following describes a fixed annuity?

A fixed annuity is characterized by providing a stable lifetime income once established, making the selection of this option accurate. In a fixed annuity, the insurer guarantees periodic payments that do not change over time, regardless of market conditions. This stability is appealing for individuals seeking predictability in their retirement income, as it allows for effective financial planning without the worry of fluctuating payments.

The other choices do not accurately represent the nature of a fixed annuity. For instance, fluctuating payments based on market performance describes variable annuities, which are subject to investment risk. Higher risk with potential for significant gains pertains to investment vehicles that involve market exposure, which is not applicable to fixed annuities. Lastly, payments determined by the annuitant's age may apply to certain types of annuities, but fixed annuities specifically guarantee a set payment amount rather than linking it directly to age. This emphasis on stability and guaranteed income is what makes option B the correct description of a fixed annuity.