Nathan, a researcher, conducts a study to find out the effects of sugar consumption on the activity level of toddlers. He categorizes the participants into two groups with equal number of participants. In a day, the members of the first group consume 50 grams of sugar, whereas the members of the second group consume 40 grams of sugar. After a week, Nathan notices that the members of the first group display more restlessness than the members of the second group do. Which of the following is the independent variable in this study?
O the members of the first group
O sugar consumption by the participants
O restlessness of the participants
O the members of the second group