During a routine check-up for a 4-year-old child, the nurse assesses the child's developmental milestones according to established norms for preschoolers. One critical area of development is the ability to engage in imaginative play and the demonstration of increased social skills such as sharing and cooperation. It is noted that for optimal growth and psychosocial development, children in this age group should maintain a ratio of at least ___ hours of physical activity to hours of sedentary time each day. Assess the recommended guideline for preschoolers regarding the balance between physical activity and screen time in this age range.