Q$.24$ The figure below shows is $3-$bit ripple couriter with $O_2$ as the MSB$.$ The flip$-$flop are rising$-$edge. trinaned. The counting direction is

$($a$)$ always down

$($b$)$ always up

$($c$)$ up or down depending on the initial state of $Q_0$ only

$($d$)$ up or down depending on the initial states of $Q_2,Q_1$ and $Q_0$

$[$GATE$-$IN:$2009]$