Kris forwards an e-mail to 5 people. each of those people forward that e-mail to 5 more people. if this happens two more times, which expression shows the total number of people who have received the e-mail, not including Kris?

A) 4 x 5
B) 1+5+5^2
C)5+5^2+5^3
D) 5+5^2+5^3+5^4