The best and most correct answer among the choices provided by the question is the third choice "The person would be unable to fully digest dairy products."
People with lactose intolerance are unable to fully digest the sugar (lactose) in milk. As a result, they have diarrhea, gas and bloating after eating or drinking dairy products. ... A deficiency of lactase — an enzyme produced in your small intestine — is usually responsible for lactose intolerance.
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