As Alyson Awaits the Birth of Her First Grandchild She

As Alyson awaits the birth of her first grandchild she says that she doesn't care if the baby is a boy or a girl as long as it is healthy. But as she holds her newborn granddaughter, Alyson says that she had known all along that it was the little girl she had hoped for! The barrier to rational reasoning illustrated by Alyson is called:

A) justification of effort.
B) mental set.
C) hindsight bias.
D) confirmation bias.