A $30\%($by volume$)$ suspension of spherical sand particles in a viscous oil has a hindered settling velocity of $4\mathrm{.}44$ m$/$s$.$ If the Richardson Zaki hindered settling index is $4\mathrm{.}5,$ then the terminal velocity of a sand grain is

$0\mathrm{.}90$ m$/$s

$1$ m$/$s

$22\mathrm{.}1$ m$/$s

$0\mathrm{.}02$ m$/$s