A

\[ \left(\frac{a}{b}\right)^3 - \left(\frac{b}{a}\right)^3 \]

B

\[a^3+ab+b^3\]

C

\[a^3+3ab+b^3\]

D

\[ \left(\frac{a}{b}\right) + \left(\frac{b}{a}\right)^3 \]

E

\[(a+b)^3\]