The formula used in this problem is [tex]f(t) = f_{1} * r^{t-1}[/tex], where r is the common ratio. The common ratio is how you get from one term to the next. In this case, the common ratio is ·4, so from one year, or term, to the next the number of frogs is multiplied by four. This makes the answer B. The number of frogs quadruples every year.
