Write the structures of A, B, and C in the following sequence of reactions:
(a) \(\text{CH}_3\text{COOH} \xrightarrow{\text{SOCl}_2} A \xrightarrow{\text{H}_2, \text{Pd-BaSO}_4} B \xrightarrow{\text{H}_2\text{N-NH}_2} C\)
(b) \(\text{CH}_3\text{CN} \xrightarrow{1.\text{DIBAL-H}} A \xrightarrow{2.\text{H}_2\text{O}} B \xrightarrow{\Delta} C\)