The following reaction constituts : `RNH_2 + S=C=S underset (H_2S) overset (H_gCl_2) (rarr) underset ("Alkyl isothicoyanate") (R-N=C=S) +H_2S`A. Mustaard ila reactionB. Test for `3^@` amineC. Test for `2^@` amineD. Test for `CS_2`