Final answer:
The presence and adequacy of lactase determine the successful digestion of lactose, leading to the condition of lactose intolerance in some individuals.
Step-by-step explanation:
The best conclusion based on the information given about the digestion of lactose is that the presence and adequacy of lactase determine the successful digestion of lactose, leading to the condition of lactose intolerance in some individuals.
Lactase is a protein located in the small intestine that is responsible for digesting lactose, a sugar found in dairy products. While many people produce enough lactase to successfully digest lactose, some people do not produce enough lactase, resulting in lactose intolerance.