Final answer:
The offspring being non-viable is most likely due to the parents being from different species, leading to hybrid sterility or hybrid inviability, where the offspring cannot reproduce or fail to survive past embryonic stages.
Step-by-step explanation:
The most likely explanation for the phenomenon where offspring are produced by two individuals but these offspring in turn produce non-viable offspring is that the parents are from different species. This situation often leads to what is known as hybrid inviability or hybrid sterility.
When different species mate, postzygotic barriers such as genetic incompatibilities may prevent proper development of the offspring. Frequently, even if the offspring reach maturity, they are unable to produce viable gametes themselves, rendering the offspring infertile. This common occurrence is known as hybrid sterility, evident in mules, which are the offspring of a female horse and a male donkey. Hybrid inviability, on the other hand, occurs when the hybrid embryos do not survive past the embryonic stages, indicating that the resulting organism is simply not viable.
Another facet of this phenomenon is inbreeding, which involves mating between closely related individuals, often leading to the combination of harmful mutations that result in less fit offspring. However, inbreeding is distinct from the scenario presented where two different species mate and produce non-viable offspring.
For example, when a horse and a donkey, which are different species, mate, they produce a hybrid called a mule. Mules are usually sterile and unable to reproduce because of genetic incompatibilities between the horse and donkey DNA.
Therefore, option 3) The parents are from different species is the most likely explanation for the phenomenon of non-viable offspring.