Đáp án đúng: B
1:2
${{M}_{{{C}_{x}}{{H}_{y}}}}\,=\,14.2\,=\,28\,gam\,\Rightarrow \,{{m}_{C}}\,=\,28.85,7{\scriptstyle{}^{o}\!\!\diagup\!\!{}_{o}\;}\,=\,23,996$
$\Rightarrow \,x\,=\,\frac{23,996}{12}\,=\,2\,\Rightarrow \,y\,=\,\frac{28\,-\,12.2}{1}\,=\,4\,\Rightarrow \,{{C}_{2}}{{H}_{4}}$