Answer:
D. sympatric populations of species with similar ecological niches.
Step-by-step explanation:
In a sympatric population, two similar species live together in the same niche but do not mate with each other. So when two species share the same niche than competition occurs between them for same resource and space.
So to avoid competition sympatric populations of species divide their niche which is called resource partitioning. This resource partitioning allows two species to co-exist.
For example, different species of lizard which feed on insects on Caribbean islands partitioned their resource by occupying different physical location to avoid competition. So the correct answer is D.