Question

healthy oceans and forests
a.
are a carbon dioxide source

b.
are a carbon dioxide sink

c.
are an example of positive feedback

d.
contribute most of the greenhouse gases

Explanation:

• Option A: Carbon dioxide sources release CO₂ (e.g., fossil fuel burning). Oceans/forests don't primarily release CO₂ in a healthy state, so A is wrong.
• Option B: Oceans absorb CO₂ (via physical/biological processes), forests absorb CO₂ through photosynthesis. So healthy oceans/forests act as CO₂ sinks, making B correct.
• Option C: Positive feedback amplifies changes. Oceans/forests absorbing CO₂ is a stabilizing (negative feedback - like) or normal carbon cycle part, not positive feedback, so C is wrong.
• Option D: Greenhouse gases (e.g., CO₂, CH₄) are mostly from human activities (fossil fuels, agriculture) or natural sources like volcanoes, not healthy oceans/forests, so D is wrong.

Answer:

B. are a carbon dioxide sink