A young patient is diagnosed with the genetic disorder lactose intolerance, which results in the inability to digest milk products due to a missing enzyme called lactase. What is most likely the cause of lactose intolerance in this patient?


A. The patient is allergic to milk.


B. The patient stopped consuming milk products.


C. A disease destroyed the lining of the patient’s small intestine.


D. A mutation occurred in the gene that is responsible for producing lactase.