Identify A, B and C in the following reactions ${\mathrm{CH}}_3\mathrm{Cl}\stackrel{\mathrm{KCN}}{⟶}\mathrm{A}\underset{{\mathrm{H}}_3{\mathrm{O}}^{\oplus }}{\overset{\mathrm{Hydrolysis}}{\to }}\underset{△}{\overset{{\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}/{\mathrm{H}}^{+}}{\to }}\mathrm{C}$
 

	A	B	C
1	${\mathrm{CH}}_{3}CN$	${\mathrm{CH}}_3{\mathrm{NHCH}}_3$	${\mathrm{CH}}_3\mathrm{N}\left({\mathrm{CH}}_3\right){\mathrm{C}}_2{\mathrm{H}}_5$
2	${\mathrm{CH}}_{3}CN$	${\mathrm{CH}}_3{\mathrm{CONH}}_2$	${\mathrm{CH}}_3{\mathrm{CO}}_2\mathrm{H}$
3	${\mathrm{CH}}_{3}CN$	${\mathrm{CH}}_3{\mathrm{CO}}_2\mathrm{H}$	${\mathrm{CH}}_3{\mathrm{CO}}_2{\mathrm{C}}_2{\mathrm{H}}_5$
4	${\mathrm{CH}}_{3}CN$	${\mathrm{CH}}_3{\mathrm{CO}}_2\mathrm{H}$	${\left({\mathrm{CH}}_3\mathrm{CO}\right)}_2\mathrm{O}$