沼气是一种能源,它的主要成分是CH₄.0.5molCH₄完全燃烧生成CO₂和水时放出445KJ热量.下列有关热化学方程式正确的是

A．2CH4(g)+4O2(g)=2CO2(g)+4H2O(l)；ΔH=+890KJ/mol

B．CH4(g)+ 2O2(g)= CO2(g)+2H2O(l)；ΔH=+890KJ/mol

C．CH4(g)+ 2O2(g)= CO2(g)+2H2O(l)；ΔH=-890KJ/mol

D．1/2 CH4(g)+O2(g)="1/2" CO2(g)+H2O(l)；ΔH=-890KJ/mol