Assess students' understanding of the carbon cycle by identifying major reservoirs (atmosphere, oceans, biosphere, soils, lithosphere), describing key fluxes (photosynthesis, respiration, decomposition, ocean uptake, sedimentation, combustion), comparing relative magnitudes/residence times, and explaining how human activities (fossil fuel burning, land-use change) alter fluxes and increase atmospheric CO2; includes interpreting a simple flux diagram and discussing climate implications and mitigation strategies.