Write the Domain in Interval Notation $$z ( a ) = \sqrt { a + 9 }$$

Multiple Choice

Write the domain in interval notation.
- $$z ( a ) = \sqrt { a + 9 }$$

A) $[ 0 , \infty )$
B) $( - \infty , \infty )$
C) $[ - 9 , \infty )$
D) $( - 9 , \infty )$