Answer:
The correct answer would be d. Coexistence
This can be explained with the help of the competitive exclusion principle which states that two species occupying the same niche cannot coexist.
It is because they would compete for the same limiting resources and thus the species which has even the slightest survival advantage over another will survive and the other would extinct.
Thus, coexistence is not a possible long-term consequence of two organisms occupying the same niche.