GKFix MCQ Question

Which reaction represents a standard formation reaction?

• A. NH₃(g) + HCl(g) → NH₄Cl(s)
• B. 2NH₃(g) → N₂(g) + 3H₂(g)
• C. 1/2 N₂(g) + 3/2 H₂(g) → NH₃(g)
• D. N₂(g) + 3H₂(g) → 2NH₃(g)