The compound formed when gypsum is dissolved in aqueous ammonium sulphate solution is:

• A
  $CaSO_4 \cdot NH_4Cl \cdot H_2O$
• B
  $CaCl_2 \cdot (NH_4)_2SO_4 \cdot H_2O$
• C
  $CaSO_4 \cdot (NH_4)_2SO_4 \cdot 2H_2O$
• D
  $CaCl_2 \cdot NH_4Cl \cdot 2H_2O$