Genes for regulatory elements, such as creb, were found to be important in animal learning. Which of the following would increase the probability that such an element is studied throughout the animal kingdom?

A) the large number of copies of the creb gene within a genome
B) its unique to Drosophila
C) the finding that creb activates odor perception
D) the finding that creb is highly conserved
E) the interaction of creb with cAMP