Using simple interest, interest is earned on -----------, while on a compound interest; the interest is earned on ------------------. Which of the following is a correct combination to fill out the blanks above in order?

a. Previously earned interest; both principal and interest received

b. Previously earned interest; only the original principal.

c. Only the original principal; previously earned interest

d. Only the original principal; both principal and interest received

e. Both principal and interest received; only the original principal