For the expression frac 2x²+28x+93/(x+6)³, which sum represents the correct form of the partial fraction decomposition?
a. A/x+6 + B/(x+6)²
b. A/x+6 + B/x+C(x+6)²
c. A/x+6 + B/(x+6)²+ C/(x+6)³
d. A/x+6 + B/x+C(x+6)²+ D/x²+E/(x+6)³