$\text { Determine all values of } x \text {, (if any), at which the graph of the function has a }$

Multiple Choice

$\text { Determine all values of } x \text {, (if any) , at which the graph of the function has a }$ horizontal tangent.
$y ( x ) = \frac { 9 } { x - 6 }$

A) $x = 9$ and $x = - 6$
B) $x = 9$
C) $x = 9$ and $x = 6$
D) $x = 6$
E) The graph has no horizontal tangents.