Determine the vertical asymptote$($s$)$ of the following function. If none exists, state that fact.

$f(x)=\frac{x+4}{x^2+6x+8}$

Select the correct choice below and, if necessary, fill in the answer box$($es$)$ to complete your choice.

A$.$ The function has one vertical asymptote, $.($Type an equation.$)$

B$.$ The function has two vertical asymptotes. The leftmost asymptote is and the rightmost asymp $($Type equations.$)$

C$.$ The function has three vertical asymptotes. The leftmost asymptote is the middle asymptote