Which of the following is true of annuities?

Select one: a. An ordinary annuity is an equal payment paid or received at the beginning of each period.

b. An annuity due is a payment paid or received at the beginning of each period that increases by an equal amount each period.

c. An ordinary annuity is an equal payment paid or received at the end of each period that increases by an equal amount each period.

d. An annuity due is an equal stream of cash flows that is paid or received at the beginning of each period.