已知:⑴ H2(g)+ 1/2 O2(g)= H2O(g);△H =" a" kJ·mol-1Ⅴ ⑵ 2H2(g)+ O2(g)= H2O(g);△H =" " b kJ·mol-1 ⑶ H2(g)+ 1/2 O2(g)= H2O(l);△H =" " ckJ·mol-1 ⑷ 2H2(g)+ O2(g)= H2O(l);△H =" d" kJ·mol-1 下列关系正确的是( )