下列热化学方程式书写正确的是 A．C(s) + O2(g) == CO2(g) ；△H= +393.5 kJ/mol B．H2(g) + 1/2O2(g) == H2O(l)；△H =－285.8 kJ/mol C．2SO2 + O2 == 2SO3 ；△H =－196.6 kJ/mol D．2H2(g) + O2(g) == 2H2O(l) ；△H =－571