The correct answer is C. Acetic acid.
Vinegar is a liquid that is made from fermented alcohol. The alcohol is usually made from grapes, but it can also be made from other fruits or vegetables. The fermentation process produces acetic acid, which gives vinegar its sour taste.
Oxalic acid is a poisonous substance that is found in some plants, such as rhubarb and spinach. It is used in some cleaning products and as a rust remover.
Hydrochloric acid is a strong acid that is used in many industrial processes. It is also used in some cleaning products and as a drain cleaner.
Citric acid is a weak acid that is found in citrus fruits. It is used as a flavoring agent in many foods and drinks.
Acetic acid is a weak acid that is found in vinegar. It is also used in some cleaning products and as a preservative.