Answer:
D. bacteria
Step-by-step explanation:
Bacteria are well-known for bacterial infections, which are definitely harmful to humans. Yet they are also helpful in that they break down organic materials. Many live in our bodies, namely E. coli, which is inside the colon breaking down our food!
- Why not A: Plantae are mostly helpful to humans because they give off O2.
- Why not B: We have little interaction with archaea; they live in extreme environments.
- Why not C: Humans are eukarya-- we can of course hurt each other, but I doubt that is what the question is looking for.