Carbon Cycle Label Sequence

Steps:

• Carbon dioxide from the air enters plants through photosynthesis (box 1: the air).
• Plants incorporate carbon into biomass (box 2: plants).
• Decomposers break down dead plant and animal matter, releasing CO2 (box 3: decomposers).
• Animals consume plants or other animals, transferring carbon (box 4: animals).

Why D is correct:

• Matches the carbon cycle's flow: atmospheric CO2 → plant fixation → decomposition release → animal consumption, per the biological definition of biogeochemical cycling.

Why the others are wrong:

• A: Starts with plants, reversing the intake from air.
• B: Places animals before decomposers, ignoring decomposition's role in carbon return.
• C: Begins with plants and inserts air second, disrupting atmospheric origin.

Final answer: D