Determine Which of the Rational Functions Given Below Has the Following

Multiple Choice

Determine which of the rational functions given below has the following feature(s) .
-The x-axis is its horizontal asymptote

A) $f ( x ) = \frac { 5 x - 1 } { x + 9 }$

B) $f ( x ) = \frac { 9 } { x - 5 }$

C) $f ( x ) = \frac { x - 5 } { x }$

D) $f ( x ) = \frac { x + 5 } { x + 9 }$