c
\(\begin{array}{l}
Suppose\,that\,the\,tennis\,ball\,bounces\,\\
with\,a\,velocity\,u.\,It\,will\,go\,up,\,its\,velocity\\
becomes\,zero.\,If\,h\,is\,the\,hgight\,up\,to\,which\\
it\,rises\,on\,the\,hill,\,then\\
\,\,\,\,\,\,\,\,\,\,\,\,{\left( 0 \right)^2} - {u^2} = 2\left( { - g'} \right)h\\
Where\,g'\,is\,acceleration\,due\,to\,gravity\,\\
on\,the\,hill.
\end{array}\)

\(\begin{array}{l}
\therefore h = \frac{{{u^2}}}{{2g'}}\\
{\rm{since}},\,the\,accleration\,due\,to\,gravity\,on\\
the\,hill\,\left( {g'} \right)\,is\,less\,than\,that\,on\,earth\,\\
\left( {effect\,of\,height} \right),\,it\,follows\,that\,tennis\\
ball\,will\,bounce\,higher\,on\,hills\,than\,in\,\\
plains.
\end{array}\)