化学反应N₂＋3H₂＝ 2NH₃的能量变化如图所示，该反应的热化学方程式是

A．N2(g)＋3H2(g) ＝ 2NH3(l)⊿H ＝ 2(a—b—c)kJ·mol^-1

B．N2(g)＋3H2(g) ＝ 2NH3(g) ⊿H ＝ 2(b—a)kJ·mol^－1

C．1/2N2(g)＋3/2H2(g) ＝ NH3(l) ⊿H ＝ (b＋c—a)kJ·mol^－1

D．1/2N2(g)＋3/2H2(g) ＝NH3(g)⊿H ＝ (a＋b)kJ·mol^－1