No two species can occupy the same niche in the same habitat at the same time a. because of the interactions that shape the ecosystem.

b. unless the species require different abiotic factors.
because of the competitive exclusion principle.

d. unless the species require different biotic factors.

the principles and empirical processes of discovery and demonstration considered characteristic of or necessary for scientific investigation, generally involving the observation of phenomena, the formulation of a hypothesis concerning the phenomena, experimentation to test the hypothesis, and development of a conclusion that confirms, rejects, or modifies the hypothesis.