The circulatory and respiratory systems interact to maintain homeostasis by
a. blood cells picking up and carrying oxygen from the lungs to the body's cells.
b. the collection and return of fluid from the lymphatic system that leaked from the blood vessels.
c. blood plasma transporting salts, sugars, fats and dissolved proteins through the body.
d. the coordination of the diaphragm and rib cage moving air into and out of the lungs.

Blood cells picking up and carrying oxygen from the lungs to the body's cells (Ans. A)

Explanation:

Red blood cells (RBC) have the main function of carrying oxygen. These cells are present in our blood & their journey begins in the lungs where they picking up & carrying oxygen from the air we breathe. Then the blood cells travel to the heart through the veins, which pump out the blood & delivering oxygen to all parts of our body.  

So, the correct option is A.