Which of the following equations are balanced? Balance those that need it. a. CaC₂+2 H₂O→Ca(OH)₂+C₂H₂ b. C₂H₈N₂+2 N₂O₄→2 N₂+2 CO₂+4 H₂O c. 3 MgO +2 Fe→Fe₂O₃+3 Mg d. N₂O→N₂+O₂