An amphibian heart is shown in the diagram.



Which statement best describes the three chambers of the heart?

Y receives oxygen-rich blood, X receives carbon dioxide–rich blood, and Z pumps blood.
Z receives oxygen-rich blood, X receives carbon dioxide–rich blood, and Y pumps blood.
X receives oxygen-rich blood, Y receives carbon dioxide–rich blood, and Z pumps blood.
Y receives oxygen-rich blood, Z receives carbon dioxide–rich blood, and X pumps blood.