#### Answer

$\bf graph(c)$

#### Work Step by Step

Given: $x^2+6x+8=0$
Need to use factorization to solve the quadratic equation.
This can be factorized as follows:
$x^2+2x+4x+8=0$
or, $(x+2)(x+4)=0$
Now $x+2=0$ and $x+4=0$
Roots are $x=-2,-4$.
These values are represented by $\bf graph(c)$