Answer:
a. habitat isolation
Step-by-step explanation:
Habitat isolation is a type of prezygotic reproductive barrier caused by differential habitat preferences, thereby lowering the probabilities of mating between individuals living in different habitats. Habitat isolation is a mechanism of ecological speciation that over time leads to divergence of populations and reproductive isolation. In habitat isolation, different species or populations that could interbreed with one another to produce offspring are prevented from mating as a consequence to be isolated by habitat barriers. In India, for example, lions and tigers can mate to produce offspring; however, they don't interbreed due to habitat barriers (tigers are found primarily in rainforests and lions inhabit the grasslands).