Find All the Real Zeros of the Polynomial Function $f ( x ) = x ^ { 2 } - 9$

Multiple Choice

Find all the real zeros of the polynomial function.​ $f ( x ) = x ^ { 2 } - 9$ ​

A) $- 9$
B) $$3$$
C) $$- 3$$
D) $9$
E) $\pm 3$