Which pair of processes drives the most direct exchange of CO₂ between living organisms and the atmosphere?
APhotosynthesis (absorbs CO₂) and cellular respiration (releases CO₂)
BPhotosynthesis (releases CO₂) and cellular respiration (absorbs CO₂)
CTranspiration (releases CO₂) and condensation (absorbs CO₂)
DNitrogen fixation (absorbs CO₂) and decomposition (releases O₂)
Explanation
Photosynthesis consumes atmospheric CO₂ to build glucose (CO₂ → sugar), while cellular respiration breaks glucose back down to CO₂ and water. Together they form the short-term carbon cycle between the biosphere and atmosphere. Distractor B reverses the direction. Transpiration moves water vapor, not CO₂. Nitrogen fixation moves nitrogen, not carbon.