Young White-Crowned Sparrows Are Remarkably Good at Remembering the Sounds

Young white-crowned sparrows are remarkably good at remembering the sounds produced by adult white-crowned males singing around them. If the learning abilities of these birds evolved by Darwinian natural selection, specific conditions must have applied to the species in the past. Which of the following statements about those conditions is incorrect?

A) There must have been variation in the memory skills of individuals.
B) Any changes that took place in the past must have promoted greater population stability in this bird.
C) Better than average song "rememberers" must have been able to pass on their abilities to their offspring.
D) Better than average song "rememberers" must have had more surviving offspring on average than the typical sparrow at that time.