In the middle of a hot summer day, Keiji and Ama stand at the bottom of a hill wearing identical backpacks. They both start to hike up the side of the steep hill. Keiji is wearing a loose cotton shirt while Ama is wearing a tight synthetic shirt. Halfway up the hill, they both take a break. Whose shirt is more likely to have visible sweat marks, and why?

Respond very briefly.
Ama's tight synthetic shirt is more likely to have visible sweat marks. The reason is that the tight fit and synthetic fabric of Ama's shirt likely do not allow sweat to evaporate as efficiently as the loose cotton fabric of Keiji's shirt. Cotton is more breathable and absorbs moisture better, allowing air to pass through and promote evaporation, which cools the body and reduces the visibility of sweat. The tight synthetic shirt worn by Ama will trap moisture against the skin, making sweat marks more visible.