Which function has a horizontal asymptote $aty=-2?$

$A.y=\frac{-2x-6}{-x-3}$

$B.y=\frac{-2x-3}{2x^2+3}$

$C.y=\frac{-2x^2-1}{2x}$

$D.y=\frac{-2x-6}{x+3}$