The figure shows the first three in a sequence of squares. The first square in the sequence has a side length of four units, and each square after that has a side length that is two units longer than the previous square.

What is the explicit equation for f(n) that represents the areas of the squares in the sequence?
A) f(n) = 4n²
B) f(n) = (4 + 2n)²
C) f(n)= (4 + 2(n-1))²
D) f(n) = 2(n-1)² +4