b
(b)
Velocity $=$ Slope of distance - Time graph
Last portion of given graph is a straight line which indicates that velocity is constant, i.e. terminal velocity is reached.
From data of graph, Terminal velocity,
$v=\frac{x_2-x_1}{t_2-t_1}=0.4-0.3$
$=\frac{0.1}{0.3}=0.33 \,m / s$
