Explanation

(b)
Acetonitriles on hydrolysis produce carboxylic acids with the evolution of ammonia.
$O$ $O$
$||$ $\ \ \ \ \ ||$
$CH_{3} - C \equiv N\overset{H_{2}O}{\rightarrow}CH_{3} - C - NH_{2}\overset{H_{2}O}{\rightarrow}CH_{3} - C - OH + NH_{3}$
Acetonitrile acetamide acetic acid