In what form do birds excrete waste materials from their bodies?

Match each part of the body to its correct organ system by writing (a), (b), (c) or (d) in the blanks.

(a) respiratory system (b) digestive system (c) circulatory system (d) excretory system

The schematic diagram represents the path taken by oxygen-rich and carbon dioxide-rich blood in our body. Label the heart and the parts that represent the pulmonary artery, pulmonary veins, aorta and vena cava.