1. (1 mark) A study of the association between physical activity and brain volume was conducted using data from the UK Biobank. Which of the following variables that were collected are categorical variables? Select all that apply. (a) Age (years); (b) Sex (female, male); (c) Sleep duration (hours); (d) Body mass Index (kg/m?); (e) Self-rated health (excellent, very good, good, fair, poor)