Many pregnant women experience symptoms of vitamin deficiencies, but this is usually not due to a lack of vitamins in the pregnant woman's diet, but due to the growth of intra-abdominal babies that make them have higher vitamin requirements than others. In order to evaluate the accuracy of the above conclusions, which of the following operations is most important? ['Test the daily diet of a pregnant woman who is not deficient in vitamins to determine the vitamin content.', 'Research on scientific recipes for pregnant women to determine the best option for pregnant women to get enough vitamins.', 'Test a pregnant woman and a non-pregnant woman who have sufficient vitamins in their daily diet and determine whether they are deficient in vitamins.', 'Test one pregnant woman and another non-pregnant woman who is deficient in vitamins in their daily diet and determine whether they are deficient in vitamins.']