Answer:
C. an investment plan that guarantees payments at regular intervals after retirement.
Explanation:
We can describe annuity as a fixed amount of money that will be paid to someone each year, for the rest of their life.
It is a long term investment, designed to help protect you from the risk of outliving your income.
The amount one pays is converted into periodic payments that can last for life.
Therefore, the correct answer is option C.