8. What is the combined primary function of the respiratory and circulatory systems?
a. Store oxygen for the body to use.
b. Supply nutrients and remove waste products from the digestion of food.
c. Protect the body from infection and regulate temperature.
d. Continuously supply body tissues and cells with oxygen.

d

The respiratory and circulatory systems bring oxygen and nutrients to the cells. The respiratory and circulatory systems work together to maintain homeostasis. The respiratory system moves gases into and out of the blood. The lungs contain the bronchi, bronchioles, and alveoli.

Explanation:

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