Multiple choice

What is NOT a source of the carbon dioxide used by plants during photosynthesis.

  1. animals exhaling

  2. plant waste

  3. wildfires

  4. volcanic activity
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Carbon dioxide is released into the atmosphere by respiration, combustion, and volcanic activity. Plant waste, such as fallen leaves, is typically decomposed by microorganisms, which releases nutrients back into the soil rather than being a primary source of atmospheric carbon dioxide for photosynthesis.

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