Niches of Single-Celled Algae, Such as Diatoms, Seem Most Often

Niches of single-celled algae, such as diatoms, seem most often to be distinguished by their requirements for

A) different combinations of inorganic nutrients.
B) different light environments.
C) different water-flow environments.
D) different water temperatures.
E) Most single-celled algae have indistinguishable niches.