In an Expedition to a Remote Part of South America

In an expedition to a remote part of South America, you find two very closely related rodent species that build very different burrows: one is shaped like a corkscrew and the other is straight. You cross individuals from the two species and observe their burrow-building behavior. Which of the following observations would allow you to conclude that this is an innate rather than a learned behavior?

A) Offspring make a burrow similar to that of their closest neighbor in the habitat.
B) Offspring make intermediate burrows that resemble those of neither parent.
C) Offspring make a burrow that is easiest to dig in the soil where they live.
D) Offspring make a burrow that is hardest for local predators to invade.