Which of the following describes hybrid infertility?

Hybrid infertility specifically refers to a situation where the offspring produced from the mating of two different species or distinct populations are viable, meaning they are born and can survive, but they are sterile, which means they are unable to reproduce. This phenomenon is commonly observed in hybrids, such as mules, which are the offspring of a male donkey and a female horse. Mules are generally healthy and capable of living a full life, but they do not possess the reproductive capabilities of either parent species.

The other choices do not accurately capture the definition of hybrid infertility. The first option discusses offspring being unable to reach adulthood, which pertains more to hybrid inviability than infertility. The third choice highlights survival in the environment, which also relates to inviability rather than fertility. The final option about mutations affecting reproductive capabilities does not specifically address the more common scenario of hybrids being sterile despite being otherwise viable. Thus, the correct answer effectively encapsulates the concept of hybrid infertility, where offspring may develop normally but lack the ability to reproduce.