Đáp án đúng: B
20 cm3 và 10 cm3.
$\begin{array}{l}C{{H}_{4}}\,+\,2{{O}_{2}}\,\xrightarrow{{{t}^{o}}}\,C{{O}_{2}}\,+\,2{{H}_{2}}O\\2{{H}_{2}}\,+\,{{O}_{2}}\,\xrightarrow{{{t}^{o}}}\,2{{H}_{2}}O\end{array}$
$\displaystyle \Rightarrow \left\{ \begin{array}{l}{{V}_{C{{O}_{2}}}}\,+\,{{V}_{{{H}_{2}}O}}\,=\,30\\2{{V}_{C{{O}_{2}}}}\,+\,0,5{{V}_{{{H}_{2}}O}}\,=\,45\end{array} \right.\,\Rightarrow \,\left\{ \begin{array}{l}{{V}_{C{{O}_{2}}}}\,=\,20\\{{V}_{{{H}_{2}}}}\,=\,10\end{array} \right.$