Which of the reactions below is a formation reaction? 1. 2 fe(s) + 3 o(g) → fe2o3(s) 2. n2(g) + 2 h2(g) + 1 2 o2(g) → n2h4o(g) 3. b2(s) + 2 i2(ℓ) + cl2(g) → 2 bi2cl(g) 4. cdiamond(s) + 1 2 o2(g) → co(g)?