Which of the following set of raw materials are used in the manufacture of $Na_2CO_3$ by Solvay process ?
( A ) $CaCl_2,\;NH_3,\;CO_2$
( B ) $NaCl, \; NH_3, \; CO_2$
( C ) $Ca(OH)_2, \; NH_3, \;CO_2$
( D ) $NaOH, \; NH_3,\;CO_2$