Final answer:
Carbon dioxide is the waste product primarily excreted by the lungs.
Step-by-step explanation:
The waste product primarily excreted by the lungs is carbon dioxide. When we breathe in, we take in oxygen, and when we breathe out, we exhale carbon dioxide. This is part of the process of respiration, where oxygen is taken in by the body's cells and carbon dioxide is produced as a waste product.
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