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: Healthy oceans and forests absorb (not emit) CO₂, so they aren't a source. Eliminate A.
• Option B: Oceans absorb CO₂, and forests (via photosynthesis) take in CO₂, acting as carbon sinks. This fits.
• Option C: They relate to carbon sequestration (negative feedback for climate, not positive feedback). Eliminate C.
• Option D: Human activities (e.g., fossil fuel burning) contribute most greenhouse gases, not oceans/forests. Eliminate D.

Answer:

B. are a carbon dioxide sink