Since we're talking about a chain reaction, I think this would be a) self-sustaining. Chain reactions are not usually described as "weak" and can be highly explosive depending upon the compounds (think Uranium!).
The first (artificial) self-sustaining nuclear reaction is attributed to Enrico Fermi in 1942. Here's a bit of history:
http://www.atomicarchive.com/History/firstpile/firstpile_01.shtml
I think thats the answer but feel free to check my work
An open system<span> is a system that has external interactions.</span>
Explanation:
The roots of trees in a forest are colonized by symbiotic fungi called mycorrhizae. These fungi are significant nitrogen fixers because they harbor nitrogen-fixing bacteria. They convert atmospheric nitrogen into nitrates and nitrites that can be absorbed by plants. The plants use these forms of nitrogen to build biomolecules such as DNA and amino acids.This nitrogen is transferred up the food chain. Eventually the nitrogen is again recycled by denitrifiers when the organisms die.
Removing trees will disrupt the symbiotic relationship with mycorrhizae, stime the nitrogen cycle in the forest.
Learn More:
For more on mycorrhizae check out;
brainly.com/question/4388098
brainly.com/question/10085468
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