The correct option is C.
Step-by-step explanation:
The parent rational function is
The vertical asymptote of this function is y-axis.
From the given graph it is clear that the vertical asymtote of the given function is x=6. It means the function is not defined for x=6.
The function is not defined at x=6 if the denominator of the function is 0 at x=6.
The function is not defined for x=6.
Therefore the correct option is C.