① C2H2(g) + 
O2(g) = 2CO2(g)＋H2O(l) ΔH1＝-1301.0 kJ•mol-1
② C(s)+ O2(g) = CO2(g) △H2＝-393.5 kJ•mol-1
③ H2(g)+ 
O2(g) = H2O(l) △H3 = -285.8 kJ·mol-1
则反应④ 2C(s)+ H2(g) = C2H2(g)的△H为（ ）
A . +228.2 kJ·mol-1
B . -228.2 kJ·mol-1
C . +1301.0 kJ·mol-1
D . +621.7 kJ·mol-1
