a
\(\begin{array}{l}
{\rm{ Instan}}{\kern 1pt} {\rm{tan}}eous\,velocity\,v = \frac{{\Delta x}}{{\Delta t}}\\
From\,graph,\,{v_A} = \frac{{\Delta {x_A}}}{{\Delta {t_A}}} = 0.5m/s\\
and\,{v_B} = \frac{{\Delta {x_B}}}{{\Delta {t_B}}} = \frac{{8m}}{{16s}} = 0.5m/s\\
i.e.,{v_A} = {v_B} = 0.5m/s
\end{array}\)