Complete the square for the expression. Write the resulting expression as a binomial squared.
x^2 + 4x + ___

A. x^2 + 4x + 4 = (x + 4)^2
B. x^2 + 4x + 16 = (x + 2)^2
C. x^2 + 4x + 4 = (x + 2)^2
D. x^2 + 4x + 16 = (x + 4)^2