C-11-Q041mediumsingle_mcqCO2+4H2→Ni, 250 ∘C?\mathrm{CO_2 + 4H_2 \xrightarrow{Ni,\ 250\,^{\circ}\text{C}} ?}CO2+4H2Ni, 250∘C?aCH4+2H2O\mathrm{CH_4 + 2H_2O}CH4+2H2ObC2H4+H2O\mathrm{C_2H_4 + H_2O}C2H4+H2OcCH3OH\mathrm{CH_3OH}CH3OHdCH3COOH\mathrm{CH_3COOH}CH3COOH