单项选择题

A.CO(g)+C(s)==CO2(g)ΔrHm1
B.CO(g)+1/2O2(s)==CO2(g)ΔrHm2
C.O2(g)+C(s)==CO2(g)ΔrHm3
D.2O2(g)+2C(s)==2CO2(g)ΔrHm4