Which statement defines an annuity?
a retirement plan offered by employers
a group of investments that many individual investors hold in common
an investment plan that guarantees payments at regular intervals after retirement\

C. An annuity is an investment plan that guarantees payments at regular intervals after retirement.

Step-by-step explanation:  

Let us see our given choices one by one.

A. A retirement plan offered by employers.

As annuities are generally offered by insurance companies, therefore, option A is not a correct choice.

B. Since a group of investments that many individual investors hold in common is called mutual funds, therefore, option B is not a correct choice.

C. An investment plan that guarantees payments at regular intervals after retirement.

Since we know that annuity is a fixed amount of money paid to someone each year for the rest of their life. Annuities are primarily used as an income stream for retirees, therefore, option C is the correct choice.