Based on the information regarding dairy products, lactose, and lactase, the hypothesis that best predicts how a change to the gene could affect people who do not produce enough lactase is:
M. A change that causes the gene to increase the amount of lactase it produces will increase a person's ability to break down lactose.
This hypothesis is the most relevant because lactase is the enzyme responsible for breaking down lactose, the sugar found in dairy products. If a person has insufficient lactase production, they typically experience difficulty digesting lactose, which can lead to symptoms of lactose intolerance. Increasing lactase production would directly improve their ability to break down lactose and thereby alleviate the symptoms associated with lactose intolerance.
The other options (P, R, S) do not directly address the issue of lactose breakdown and suggest effects that are not associated with lactase's primary function.