An annuity due is:

a.	A series of equal beginning-of-period payments.
	b.	A payment due to be deposited today to cover a future retirement annuity.
	c.	A loan payment schedule with the interest paid periodically and the principal due at maturity.
	d.	A series of equal periodic payments made at the end of each period.
	e.	An account payable required to be paid today.