$\textrm{Assume there age ratio is x}$
$\textrm{then age of 3 person is $4x$,$7x$ ,$9x$}$
$\textrm{According to the question,8 year ago sum of their age was 56}$
$\Rightarrow$ $\textrm{$(4x-8)$+(7x-8)+(9x-8)=56}$
$\Rightarrow$ $20x-24=56$
$\Rightarrow$ $20x=80$
$\Rightarrow$ $x$ = $4$
$\textrm{Now their present age is16,28,36. Option B.}$