c
\(\begin{array}{l}
According\,to\,question,\,object\,is\,moving\,with\\
{\rm{constant}}\,nagative\,acceleration\,i.e.,a = - {\rm{constant}}\left( C \right)\\
\frac{{vdv}}{{dx}} = - C\\
vdv = - Cdx\\
\frac{{{v^2}}}{2} = - Cx + k\\
x = - \frac{{{v^2}}}{{2C}} + \frac{k}{C}\\
Hence\,graph\,\left( 3 \right)\,represents\,correctly
\end{array}\)