Đáp án đúng: C 0,4 lít $\begin{array}{l}{{n}_{{{H}^{+}}\,(\text{dd}\,{{H}_{2}}S{{O}_{4}})}}\,=\,0,2.2\,=\,0,4\,\Rightarrow \,{{n}_{O{{H}^{-}}\,(\text{dd}\,Ba{{(OH)}_{2}})}}\,=\,0,4\,mol\\\Rightarrow \,{{n}_{Ba{{(OH)}_{2}}}}\,=\,0,2\,mol\,\Rightarrow \,V\,=\,0,4\,lit\end{array}$