Vertical asymptote:
A vertical asymptote is a value of x for which the function is not defined, that is, it is a point which is outside the domain of a function;
In a graphic, these vertical asymptotes are given by dashed vertical lines.
An example is a value of x for which the denominator of the function is 0.
In this graphic:
Dashed vertical lines at: [tex]x = -3, x = 7[/tex], thus, for [tex]x - (-3) = x+3[/tex] and [tex]x - 7[/tex] the denominator is zero.
Thus, the function graphed is:
[tex]F(x) = \frac{1}{(x+3)(x-7)}[/tex]
And the correct answer is given by option C.
To take a look at a problem with asymptote, you can check this item https://brainly.com/question/4084552.
