In the hardening stage of plaster of paris,the compound formed is

Question

$\begin{array}{1 1}(a)\;CaSO_4\\(b)\;Orthorhomic\; CaSO_4.2H_2O\\(c)\;CaSO_4.H_2O\\(d)\;Monoclinic\;CaSO_4.2H_2O\end{array}$