Determine Whether the Function Is a Polynomial Function $$f ( x ) = \frac { 9 - x ^ { 3 } } { 5 }$$

Determine whether the function is a polynomial function.
- $$f ( x ) = \frac { 9 - x ^ { 3 } } { 5 }$$

A) 3
B) $- \frac { 1 } { 5 }$
C) 0
D) 9