Lactic acid is a: A. Three-carbon molecule B. One-carbon molecule C. Two-carbon molecule D. Four-carbon molecule

The correct answer is: A. Three-carbon molecule.

Lactic acid is a three-carbon molecule with the chemical formula C3H6O3. It is a colorless, odorless, and sour-tasting liquid that is produced when the body breaks down glucose for energy. Lactic acid is also found in milk and other dairy products.

Option B is incorrect because lactic acid is not a one-carbon molecule. Option C is incorrect because lactic acid is not a two-carbon molecule. Option D is incorrect because lactic acid is not a four-carbon molecule.