Susie is 25 years old and currently exercises for 1 hour and 30 minutes a week, using a moderate-intensity aerobic exercise. she does not participate in any muscle-strengthening exercises. what changes should she make to her exercise routine to meet the physical activity guidelines? a) decrease her current routine by 30 minutes and increase high-intensity exercise to a total of 30 minutes a week. b) increase total aerobic exercise to 2 hours and 30 minutes a week and include muscle-strengthening exercise on two or more days a week. c) maintain her current aerobic exercise routine, but add in two or more days of muscle-strengthening exercises a week. d) susie should only do vigorous intensity exercises for 45 minutes a week and muscle-strengthening exercises on two or more days a week.