Cells are the most simple level of organization, as tissues contain cells, organs contain tissues and systems contain organs, so R would be your answer.
The most specific would be felis catus. That is the name of the species in biology, and there are no more taxonomic divides after species.
Plants, Dinosaurs and bugs.
Nerves are cells that can detect any type of pressure, movement, or anything of that nature. If we didn't have nerves, we couldn't feel pain. If the nerves in a foot are damaged, you wouldn't feel the pain of it being burned.
Answer:
I believe the answer is d
