One Way to Understand How Early Environment Influences Behaviors in Similar

One way to understand how early environment influences behaviors in similar species is through the "cross-fostering" experimental technique. Suppose that the curly-whiskered mud rat differs from the bald mud rat in several ways, including being much more aggressive. Which of the following would be the best cross-fostering experiment to determine, if environment plays a role in the curly-whiskered mud rat's aggression?

A) Cross curly-whiskered mud rats and bald mud rats and hand-rear the offspring to see if any grew up to be aggressive.
B) Place newborn curly-whiskered mud rats with bald mud rat parents and place newborn bald mud rats with curly-whiskered mud rat parents. Finally, let some mud rats of both species be raised by their own species. Then you would compare the outcomes.
C) Remove the offspring of curly-whiskered mud rats and bald mud rats from their parents, raise them in the same environment but without parents, and then compare the outcomes.
D) Replace normal newborn mud rats with deformed newborn mud rats to see if it triggered an altruistic response.