# One ml of $H_2O_2$ solution gives 50ml of $O_2$ at NTP,so it is

$\begin{array}{1 1}(a)\;10vol\\(b)\;25vol\\(c)\;50vol\\(d)\;100vol\end{array}$

One ml of $H_2O_2$ solution gives 50ml of $O_2$ at NTP,so it is 50vol
Hence (c) is the correct option.