$Al_2 O_3$ can be converted to anhydrous $AlCl_3$ by heating:-

Question

( A ) $Al_2O_3$ with $HCl$ gas
( B ) $Al_2O_3$ with $Cl_2$ gas
( C ) $Al_2O_3$ with $NaCl$ in solid state
( D ) A mixture of $Al_2O_3$ and carbon in dry $Cl_2$ gas