What benefits led to natural selection of a two-circuit pump function of the heart
a) One circuit to go from the heart to the body and one from the heart to the lungs
b) One circuit to go from the heart to the body and one from the heart to the gills
c) One circuit to go from the heart to the lower body and one from the heart to the head
d) One pump to blood to the tissues and one pump to pump it back
e) To pump twice as much blood