已知C2H2(g)+5/2O2(g)=H2O(l)+2CO2(g)⊿rHmɵ,1C(s)+O2(g)=CO2(g)⊿rHmɵ,2H2(g)+1/2O2(g)=H2O(g)⊿rHmɵ,3则⊿fHmɵ(C2H2,g)与⊿rHmɵ,1、⊿rHmɵ,2、⊿rHmɵ,3的关系为( )
A. ⊿fHmɵ(C2H2,g)=⊿rHmɵ,1+⊿rHmɵ,2+⊿rHmɵ,3
B. ⊿fHmɵ(C2H2,g)=2⊿rHmɵ,2-⊿rHmɵ,1-⊿rHmɵ,3
C. ⊿fHmɵ(C2H2,g)=2⊿rHmɵ,2+⊿rHmɵ,1+⊿rHmɵ,3
D. ⊿fHmɵ(C2H2,g)=2⊿rHmɵ,2-⊿rHmɵ,1+⊿rHmɵ,3