Answer: A. Only one population will thrive; the other population will decrease to zero.
The competitive exclusion principle also known as Gause's law , states that two species which thrive for the same resources cannot coexist. Out of the two species one has extra advantageous characteristics to survive for long than the other. For survival species undergo evolutionary adaptations and increases chances of survival. Here, abiotic factors such as temperature and water supply are kept constant therefore has no affect on populations growth and extinction but food in the form of essential requirement for survival can be a competing factor for both species. Species with more adaptation and higher competing tendency will survive and weaker competing species will extinct.