Brett has been studying a type of bacteria that doubles every month. Originally, there were 5 bacterial cells. He wants to know how many there will be after 42 months. Which equation should he use?

A a42 = 5(2)42 - 1

B a42 = 5(2)(42)

C a42 = 5(2)42

D a42 = 5(2)(42 - 1)