Need help now I am doing a quiz

Ecosystems involve living organisms interacting with non-living things in a productive way; how is photosynthesis an example of this? answer, i will give brainiest to first person to get it right.

2. given that most biochemical (other than coal) rocks react with hydrochloric acid, what does that tell you about organisms?

If a strand of dna has 35% thymine. what is the percentage of cytosine, adenine, guanine?