What is the result of 16x^4 + 32x^3 + 24x^2 + 8x + 1 divided by 2x + 1?
a. x^3 + 3x^2 + 3x + 1
b. 8x^3 + 12x^2 + 6x + 1
c. x^3 + 6x^2 + 4x
d. 4x^3 + 6x^2 + 4x + 1