c
$s = {v_o}t + \frac{1}{2}a{t^2}$
$h = 0 + \frac{1}{2}(9.8){(2)^2} = 19.6\,m$
$\frac{{\Delta h}}{h} = \pm 2\left( {\frac{{\Delta t}}{t}} \right)$ $(\because {a = g}$ constant$)$
$ = \pm 2\left( {\frac{{0.1}}{2}} \right) = \pm 0.1\,$
$\therefore \Delta h= \pm \frac{h}{{10}} = \pm \frac{{19.6}}{{10}}= \pm 1.96\,m$