Which one of these best defines an annuity due?

An annuity due is a stream of unending, equal payments that are paid at equal intervals of time.

An annuity due is a stream of equal payments paid at the beginning of each equal time interval for a set number of time periods.

An annuity due is a set of unending payments that are paid over equal intervals of time.

An annuity due is a stream of equal payments with each payment occurring at the end of a set number of equal time intervals.