今有如下三个热化学方程式:
\(\rm{H_{2}(g)+ \dfrac {1}{2}O_{2}(g)═H_{2}O(g)\triangle H=a}\) \(\rm{kJ⋅mol^{-1}}\)
\(\rm{H_{2}(g)+ \dfrac {1}{2}O_{2}(g)═H_{2}O(l)\triangle H=b}\) \(\rm{kJ⋅mol^{-1}}\)
\(\rm{2H_{2}(g)+O_{2}(g)═2H_{2}O(l)\triangle H=c}\) \(\rm{kJ⋅mol^{-1}}\)
关于它们的下列表述,正确的是\(\rm{(}\) \(\rm{)}\)