题目内容：

已知：①4NH3(g)+5O2(g)=4NO(g)+6H2O(g)△H1=-akJ·mol-1

②4NH3(g)+3O2(g)=2N2(g)+6H2O(g)△H2=-bkJ·mol-1

③H2(g)+1/2O2(g)=H2O(g)△H3=-ckJ·mol-1

④H2(g)+1/2O2(g)=H2O(l)△H4=-dkJ·mol-1

下列叙述正确的是（    ）

A. 由上述热化学方程式可知△H3＜△H4

B. H2的燃烧热为dkJ·mol-1

C. 4NH3(g)+4O2(g)=2NO(g)+N2(g)+6H2O(g)△H=(-a-b)kJ·mol-1

D. 4NH3(g)2N2(g)+6H2(g)△H=(6d-b)kJ·mol-1