I think the answer is enzyme
Answer:
plant leaves contain openings called stomata, which allow the diffusion of gas exchange
A testable question is B. If a plant is turned upside down, which way will the roots grow?
The other options are incorrect because you cannot create some kind of experiment to prove them right or wrong.
Hope that helped you.
Answer:
As well as the vivid beauty that comes with great diversity in plants and animals, rainforests also play a practical role in keeping our planet healthy. By absorbing carbon dioxide and releasing the oxygen that we depend on for our survival. The absorption of this CO2 also helps to stabilize the Earth's climate