The most likely body systems that are functioning improperly in the sick birds are the circulatory and respiratory systems. Therefore, the correct answer is circulatory and respiratory.
These systems are closely related and play a crucial role in the transport of oxygen and carbon dioxide in the body.
In this case, the shortage of dissolved oxygen and a buildup of dissolved carbon dioxide in the cells suggest a problem with the respiratory system, which is responsible for the exchange of gases (oxygen and carbon dioxide) between the air and the blood. The circulatory system, on the other hand, is responsible for transporting these gases to and from the cells.
Therefore, the correct answer is circulatory and respiratory