Answer:
D. Allopatric
Step-by-step explanation:
Allopatric speciation is the process of formation of new species from the populations that live in different habitats. In the given example, one population resides on rocky islands and is adapted to the surroundings while the other population lives on the mainland.
Accumulation of genetic variations among the individuals of these geographically isolated populations would isolate them reproductively.
Since both the populations are present in different habitats, it represents the allopatric speciation.