∙ Vinegar contains acetic acid. So the acid in option A is correctly matched with its source.
∙ Curd contains lactic acid. Formic acid is present in the sting of honey bees and ants. So the acid in option B is incorrectly matched with its source.
∙ Amla contains ascorbic acid. So the acid in option C is correctly matched with its source.
∙ Citrus fruits such as lemons contain citric acid. So the acid in option D is correctly matched with its source.