反应N₂＋3H₂＝2NH₃的能量变化如图，其热化学方程式正确的是

A．N2(g)＋H2(g)＝NH3(l)ΔH＝＋(b＋c－a)kJ·mol^－1

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

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

D．N2(g)＋H2(g)＝NH3(g)ΔH＝＋(a＋b)kJ·mol^－1