化学反应N₂＋3H₂＝ 2NH₃的能量变化如下图所示，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