What situation results from a postfertilization barrier to reproduction? what situation results from a postfertilization barrier to reproduction? gamete incompatibility mechanical isolation of a species mutations in genes that control development offspring that fail to develop?

I believe the answer is Offspring that fail to develop. Post-fertilization barriers is where fertilization occurs but hybrid cannot reproduce. There two types of post fertilization barriers; Hybrid in-viability where the Zygote cannot complete development b/c genetic instructions are incomplete. The other one is Hybrid sterility where the hybrid organism cannot produce offspring b/c chromosome number is odd. 

Abay where the river empties into the sea