Which one of the following acids is present in sour milk products ?

Acetic Acid
Butyric Acid
Tartaric Acid
Lactic Acid

The correct answer is (d) Lactic Acid.

Lactic acid is a type of organic acid that is produced when bacteria convert sugar into energy. It is found in sour milk products, such as yogurt and cheese, as well as in sauerkraut and kimchi. Lactic acid is also produced in the muscles during exercise.

Acetic acid is the main component of vinegar. It is also found in some fruits and vegetables. Butyric acid is a type of fatty acid that is found in butter and other dairy products. Tartaric acid is a type of organic acid that is found in grapes and other fruits.

Lactic acid is a weak acid that has a sour taste. It is used in food as a preservative and flavoring agent. It is also used in cosmetics and pharmaceuticals.