I don’t understand it

So I believe these are the questions to go with the statement based on the info given to make a question (hypothesis) , I believe it’s “A” because based on the statement it give details about the one of them being able to drink water that contains fluoride salts and the other doesn’t drink water with fluoride salt . And we don’t know where they live , or even who drinks the fluoride salts or no so “A” is a appropriate question to give . And the numerical data part can also include the people who lives in their neighborhoods .

Hope this helps☺️