Assess students' understanding of how the respiratory and circulatory systems coordinate during physical activity; include explanation of oxygen and carbon dioxide exchange, changes in breathing rate and heart rate, the role of hemoglobin and capillaries in oxygen transport, and how increased muscular demand alters gas exchange and blood flow. Questions should require short explanations, cause-effect reasoning, and interpretation of simple rest-versus-exercise data (e.g., heart rate or breathing rate graphs).