A survey found that the incidence of cancer was higher in areas where milk consumption per capita was high, and the incidence of cancer was extremely low in areas where milk consumption per capita was low. Some people have concluded that drinking milk will cause cancer The rate goes up. Which of the following, if true, would most challenge the above conclusions? ['Regions with a high incidence of cancer, relatively low incidence of other diseases.', 'Milk has high calcium content, is well absorbed, and drinking milk before bed helps sleep.', 'The regions with large per capita milk consumption in the survey also have relatively large populations.', 'Residents in areas with a large per capita consumption of milk live longer, and the majority of people suffering from cancer are middle-aged and elderly.']