Assess understanding of the global carbon cycle by testing identification and roles of major reservoirs (atmosphere, oceans, biosphere, soils, lithosphere), typical magnitudes and timescales of natural fluxes, key exchange processes (photosynthesis, respiration, ocean uptake, weathering), and how human activities (fossil fuel combustion, land-use change, cement production) alter fluxes, sink capacities, and atmospheric CO2 concentrations; may include interpreting flux diagrams and explaining feedbacks and mitigation implications.