Answer:
Primary producers
Explanation:
Phytoplankton belong to the <u><em>primary producers</em></u> trophic level. Beings of the other levels gain energy from phytoplankton. Phytoplankton are also capable of transforming inorganic carbon into protoplasm.
D. I or Iodine
This is because they are both in the same periodic family (the halogens) and thus the number of valence electrons are the same
These are related but can be independent, because it is possible to, the theories are studied in mathematical logic, especially in model theory