Answer : (c) $\;9.7\;MJkg^{-1}$
Explanation :
Initial energy of ball = $\;mgh=m \times 9.8 \times 1000 \times 10^{3}$
$=9.8 m \times 10^{6} J$
This energy heats up the ball to $\;1125^{0}C\;$ & meets it
$9.8 \times 10^{6}=m \times 100 \times (1125-25)+m \times L$
$9.8 \times 10^{6}=100 \times 1100 +mL$
$9.8 \times 10^{6}=0.11\times10^{6}+L$
$L=9.69 \times 10^{6} J kg^{-1}\;.$