Which of the following reactions correctly represent the products formed upon heating?
$(a) \ NH_4NO_2 \xrightarrow{\Delta } N_2 + 2H_2O$
$(b) \ NH_4NO_3 \xrightarrow{\Delta } N_2O + 2H_2O$
$(c) \ Na_2CO_3 \xrightarrow{\Delta } Na_2O + CO_2$
$(d) \ NH_4Cl \xrightarrow{\Delta } NH_3 + HCl$

• A
  only $a$
• B
  $a, b, c, d$
• C
  $a, b, d$
• D
  $a, c, d$