2g氢气完全燃烧生成液态水时可放出285.8KJ的热量，下列热化学方程式正确的是

A．2H2(g)+O2(g)==2H2O(g)△H=-571.6kJ/mol

B．2H2(g)+O2(g)==2H2O(l)△H=-285.8kJ/mol

C．H2+1/2 O2==H2O△H=-285.8kJ/mol

D．2H2(g)+O2(g)==2H2O(l)△H=-571.6kJ/mol