Nutritionists believe that a person' s daily requirement for vitamins can readily be met by eating five servings of fruits and vegetables daily. However, most people eat far less than this. Thus, most people need to take vitamin pills. Which one of the following statements, if true, most seriously weakens the argument? ['Fruits and vegetables are also important sources of fiber, in forms not found in vitamin pills.', 'Many commonly consumed foods that are neither fruits nor vegetables are fortified by manufacturers with the vitamins found in fruits and vegetables.', 'Certain commonly available fruits and vegetables contain considerably more nutrients than others.', 'Nutritionists sometimes disagree on how much of a fruit or vegetable constitutes a complete serving.']