# $2D_2O\quad\underrightarrow{\text{Electrolysis}}\quad A+B$. $A+B$ are
$\begin{array}(a)\;2D_2+O_2&(b)\;D_2+O_3\\(c)\;2D_2O+O_2&(d)\;D_2O+O_3\end{array}$