Đáp án đúng: C
50%.
$\begin{array}{l}{{n}_{{{H}_{2}}O}}\,=\,\frac{18x}{18}\,=\,x\,mol;\\{{n}_{ankan}}\,=\,{{n}_{{{H}_{2}}O\,\,(ankan)}}\,-\,{{n}_{C{{O}_{2}}\,(ankan)}}\\{{n}_{ankin}}\,=\,{{n}_{C{{O}_{2}}\,(ankin)}}\,-\,{{n}_{{{H}_{2}}O\,(ankin)}}\\{{n}_{C{{O}_{2}}}}\,=\,{{n}_{{{H}_{2}}O}}\,\Rightarrow \,{{n}_{ankan}}\,=\,{{n}_{ankin}}\,\Rightarrow \,{\scriptstyle{}^{o}\!\!\diagup\!\!{}_{o}\;}{{V}_{C{{H}_{4}}}}\,=\,50{\scriptstyle{}^{o}\!\!\diagup\!\!{}_{o}\;}\end{array}$
