In the cardiac cycle,
a. the right atrium and the right ventricle contract simultaneously.
b. the two atria relax while the two ventricles contract.
c. the left atrium contracts before the right atrium.
d. all four chambers of the heart contract at the same time.
e. all four chambers of the heart are in systole at the same time.

an adaptation is a change or process by which an organism takes to be better suited for its environment. for example; migration is a behavioral adaptation, this is needed because birds are not built to last extremely cold climates. there are different adaptations because there are different species needing to adjust to different things, bears don't migrate; they hibernate.