What Is the Most Common Reason for the Disappearance of a Hybrid

What is the most common reason for the disappearance of a hybrid zone, resulting in the completion of the speciation process?

A) when hybrids are at a selective disadvantage compared to offspring from within-population matings
B) when hybrids have a selective advantage and replace the parent species
C) when hybrids are found in ring species and no longer mate with the parent species
D) when hybrids mate assortatively