Harold decides to invest some of his salary in a savings account which compounds interest semiannually. His account balance after t years can be given by the following expression. 7,021(1.035)^2t
What does the base, 1.035, represent?

A. the number of times the account interest has compounded
B. the growth factor which reveals the rate at which the account balance increases
C. amount of the yearly savings
D. the initial amount invested