Final answer:
Option (A), Species pairings that lead to miscarriage exemplify genetic incompatibility, often resulting from prezygotic barriers like reproductive organ mismatch and gametic incompatibility, which are mechanisms of natural selection.
Step-by-step explanation:
The pairings of species that always lead to miscarriage or failure to survive the embryonic stage can be categorized as an example of genetic incompatibility. This is due to various reproductive barriers that can occur prior to fertilization, known as prezygotic barriers.
Other forms of prezygotic barriers include differences in mating rituals, reproductive organ incompatibility, and gametic barriers where different species' gametes cannot fuse. The repeated occurrence of such unsuccessful pairings can lead to the reinforcement of divergence between species, maintaining species separation through natural selection, a key component of evolutionary theory.