A mixture containing primary, secondary and tertiary amine is treated with diethyl oxalate. Choose the correct statement
A. The distillate of the mixture after treatment mainly contains `1^(2)` amine.
B. `3^(@)` amine do not react with diethyl oxalate
C. This is Hinsberg method of separating `1^(@), 2^(@)` & `3^(@)` amines.
D. `3^(@)` amine is removed by filtration