What is the primary cause of Lactose intolerance in individuals with Metabolic and Nutritional Disorders?

A Lack of lactase enzyme
B Insufficient absorption of calcium
C Impaired glucose metabolism
D Deficiency of vitamin D
Lactose intolerance occurs when the small intestine does not produce enough lactase enzyme to break down lactose, a sugar found in milk and other dairy products.
Lact = Lack → lack of lactase
Guyton and Hall Textbook of Medical Physiology
Metabolic and Nutritional Disorders Nutrition and Metabolism Carbohydrate Metabolism Easy MEDICAL Confidence: high