Select the incorrect statement.

• A
  Solubility of carbonates of alkali metal cations increases down the group.
• B
  Melting point of fluorides of $Na^{+}$,$K^{+}$,$Rb^{+}$,$Cs^{+}$ decreases down the group.
• C
  Thermal stability of nitrates of group-$1$ cations decreases down the group.
• D
  Solubility of bicarbonates follows the order $Na^{+} < K^{+} < Rb^{+} < Cs^{+}$.