d
Particle velocity $\left(\mathrm{v}_{\mathrm{p}}\right)=-\mathrm{v} \times$ slope of the graph at that point
At point $1:$ Slope of the curve is positive, hence particle velocity is negative or downward $(\downarrow)$
At point $2:$ Slope negative, hence particle velocity is positive or upwards $( \uparrow)$
At point $3:$ Again slope of the curve is positive, hence particle velocity is negative or downward $(\downarrow)$