Question: Which of these are pre-zygotic isolating mechanisms? (Select all that apply.) Need Assignment Help? Question options: Two closely-related species occupy different habitats and do not encounter one another. Two closely-related species hybridize to create viable offspring, but the offspring are sterile (cannot produce offspring of their own). Two closely-related species are so different in size that mating between them is impossible. Two closely-related species mate but cannot produce viable offspring.