Carbon cycle processes and atmospheric CO2 levels

Steps:

• Identify combustion: burning fuels releases CO2 into the atmosphere, increasing levels.
• Identify photosynthesis: plants absorb CO2 to produce glucose, decreasing atmospheric levels.
• Identify respiration: organisms break down glucose, releasing CO2, increasing atmospheric levels.
• Match sequence to choices: combustion (increases), photosynthesis (decreases), respiration (increases).

Why B is correct:

• B aligns with biological definitions: combustion and respiration emit CO2 (C + O2 → CO2; C6H12O6 + 6O2 → 6CO2 + 6H2O), while photosynthesis consumes it (6CO2 + 6H2O → C6H12O6 + 6O2).

Why the others are wrong:

• A incorrectly suggests respiration decreases CO2, ignoring its release during energy production.
• C wrongly shows combustion decreasing CO2, opposite to its emission from burning carbon compounds.
• D mistakenly depicts all processes reducing CO2, overlooking emissions from combustion and respiration.

Final answer: B