The function p(d) = 5.4^d-1 represents the number of people who receive a certain email on day d of an email experiment. What does the value 5 represent in this situation?
A) There are 5 people running the experiment.
B) 5 people received the email on the first day of the experiment.
C) Every day, the number of people receiving the email increases by 5.
D) Every day, the number of people receiving the email increases by 5%.