Find the Domain of the Function $g ( p ) = \sqrt { 81 - p ^ { 2 } }$

Multiple Choice

Find the domain of the function. $g ( p ) = \sqrt { 81 - p ^ { 2 } }$

A) -9 $\le$ p $\le$ 9
B) p $\le$ -9 or p $\ge$ 9
C) p $\ge$ 0
D) p $\le$ 9
E) all real numbers