From these studies, which of the following may be considered a variable that can have a probability distribution? [I] Percentage of Sub-Saharan Africans that smoke [II] Percentage of all Sub-Saharan Africans considered obese [III] Percentage of coronary artery disease cases, in the surveyed group, caused by smoking [IV] Percentage of coronary artery disease cases, in the surveyed group, caused by obesity [V] Mean BMI of all Africans aged 60 years and older [VI] Mean BMI of a group of 100 Africans aged 60 years and older