The starting material for convenient preparation of deuterated hydrogen peroxide \( \mathrm{(D_2O_2)} \) in laboratory is:
\( \mathrm{K_2S_2O_8} \)
\( \mathrm{BaO} \)
\( \mathrm{BaO_2} \)
\( \mathrm{2\text{-}ethylanthraquinol} \)