Recall how oxidation and hydrolysis of nitriles or esters produce carboxylic acids.
Recall the reactions by which carboxylic acids can be produced: a) oxidation of primary alcohols and aldehydes with acidified K2Cr2O7 or acidified KMnO4 and refluxing b) hydrolysis of nitriles with dilute acid or dilute alkali followed by acidification c) hydrolysis of esters with dilute acid or dilute alkali and heat followed by acidification