Find the Specified Domain and Express It in Interval Notation $f ( x ) = \sqrt { x - 3 }$

Multiple Choice

Find the specified domain and express it in interval notation.
-For $f ( x ) = \sqrt { x - 3 }$ and $g ( x ) = x - 7$ , what is the domain of $g / f$ ?

A) $( 3,7 ) \cup ( 7 , \infty )$
B) $( 3 , \infty )$
C) $[ 3 , \infty )$
D) $[ 3,7 ) \cup ( 7 , \infty )$