One Way to Understand How Early Environment Influences Differing Behaviors

One way to understand how early environment influences differing 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. How would you set up a cross-fostering experiment to determine if environment plays a role in the curly-whiskered mud rat's aggression?

A) You would cross curly-whiskered mud rats and bald mud rats and hand-rear the offspring.
B) You would place newborn curly-whiskered mud rats with bald mud rat parents, place newborn bald mud rats with curly-whiskered mud rat parents, and let some mud rats of both species be raised by their own species. Then compare the outcomes.
C) You would remove the offspring of curly-whiskered mud rats and bald mud rats from their parents and raise them in the same environment.
D) You would see if curly-whiskered mud rats bred True for aggression.
E) None of these schemes describes cross-fostering.