Scientists have tried raising endangered whooping cranes in captivity by using sandhill cranes as foster parents. This strategy is no longer used because
A) fostered whooping crane chicks did not develop the necessary cues for migration.
B) the fostered whooping cranes' critical period was variable such that different chicks imprinted on different "mothers."
C) sandhill crane parents rejected their fostered whooping crane chicks soon after incubation.
D) none of the fostered whooping cranes formed a mating pair-bond with another whooping crane.
E) sandhill crane parents did not properly incubate whooping crane eggs.
