When the ranges of two different species meet, a stable 'hybrid zone' occupied by hybrid individuals may form. How is this possible? a. Two diverged populations are capable of mating and producing viable and fertile offspring. b. Hybrid individuals are always allopolyploid and are thus unable to mate with either of the original species. c. Hybrid individuals may have reduced fitness and thus be strongly selected against. d. One species has a selective advantage, so as hybridization continues, the other species will go extinct.

Verified step by step guidance

1. Identify the correct concept: A hybrid zone is an area where two different species meet and interbreed, producing hybrid offspring. Understanding this concept will help in choosing the correct answer.
2. Analyze option a: This option suggests that two diverged populations can mate and produce viable and fertile offspring. This is a key requirement for the formation of a stable hybrid zone, as it allows for the ongoing production of hybrid individuals.
3. Analyze option b: This option states that hybrid individuals are always allopolyploid and thus unable to mate with either of the original species. This is incorrect as not all hybrids are allopolyploid; many are capable of reproducing with one or both parent species.
4. Analyze option c: This option suggests that hybrid individuals may have reduced fitness and thus be strongly selected against. While this can occur, it does not explain the formation of a stable hybrid zone where hybrids continue to exist.
5. Analyze option d: This option suggests that one species has a selective advantage, leading to the extinction of the other species as hybridization continues. This does not support the formation of a stable hybrid zone but rather the dominance of one species over the other.