An aqueous solution of a colourless metal sulphate $M$ gives a white precipitate with $NaOH$. This precipitate is soluble in excess of $NaOH$. On passing $H_2S$ through this solution,a white precipitate is formed. The metal $M$ in the salt is:

• A
  $Ca$
• B
  $Ba$
• C
  $Al$
• D
  $Zn$