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 absorb, not release, so A is wrong.
• Option B: A carbon sink absorbs CO₂. Oceans dissolve CO₂, forests use it in photosynthesis, so healthy oceans/forests are sinks. This is correct.
• Option C: Positive feedback amplifies changes. Oceans/forests stabilizing CO₂ is negative feedback (or just sinks), so C is wrong.
• Option D: Greenhouse gases (e.g., CO₂, CH₄) are mostly from human activities (fossil fuels, agriculture), not oceans/forests, so D is wrong.

Answer:

B. are a carbon dioxide sink