Sunlight is the source of energy for nearly all ecosystems. Most ecosystems are found on land instead of in water. Carbon dioxide is more available than other gases. The producers in all ecosystems are plants.
I gave my students this multiple choice question: Which statement best explains why photosynthesis is the foundation of most food webs?

Only one answer is correct among these 4 choices:
- Sunlight is the source of energy for nearly all ecosystems.
- Most ecosystems are found on land instead of in water.
- Carbon dioxide is more available than other gases.
- The producers in all ecosystems are plants.

Could you tell me which one is correct?

Sunlight is the source of energy for nearly all ecosystems.