The bark of a tree is impervious to gases and water because bark cells are dead cells of the epidermis and compactly arranged without intercellular spaces. They contain a chemical called suberin in their walls that make them impervious to gases and water and it doesn't allow gases or water into the tree as bark cells are in the bark outer most layer of the tree.
Answer:
Parasitism
ExplanatioThe flatworm seems to be the only one benefitting from the relationship because it is using the snail as a host and provides it a place to grow but the snail is being harmed by the worm while doing so. Therefore the relationship is parasitic.
I would asy thd answer would be d if its not my bad .
D because they are complete systems
Are you sure these are the only answer choices? I believe the answer would be Hippocampus, but it's not up there.
