a)CH4(g)+CO2(g)⇌2CO(g)+2H2(g) ΔH1
b)CO2(g)+H2(g)⇌CO(g)+H2O(g) ΔH2
c)CH4(g)⇌C(s)+2H2(g) ΔH3
d)2CO(g)⇌CO2(g)+C(s) ΔH4
e)CO(g)+H2(g)⇌H2O(g)+C(s) ΔH5
上述反应体系在一定条件下建立平衡后,下列说法正确的有( )