B) a smokestack for an electric power plant
The 30 million years ago, because its the closest one to us. Wait is there a picture to it ?
Answer: B
Explanation:
"Furthermore, ectomycorrhizal fungi can slow down decomposition, a natural process that returns carbon from forest soils back to the atmosphere. In these ways, ectomycorrhizal fungi enhance the ability of forests to keep carbon locked up in trees and soils, and out of the atmosphere." (http://www.bu.edu/articles/2018/4-things-to-know-about-fungi-climate-warriors/)