Select the correct statement.

• A
  When a solution of alkali metal in liquid $NH_3$ is left standing,all alkali metals form stable amides.
• B
  The intensity of the blue colour of the liquid ammonia solution of alkali metal increases on increasing the concentration of the metal.
• C
  The paramagnetic character of alkali metal in liquid $NH_3$ solution increases on increasing the concentration of the metal.
• D
  The blue colour of alkali metal in liquid $NH_3$ solution is due to the absorption of orange radiation.