Answer:
Your heart is a single organ, but it acts as a double pump. The first pump carries oxygen-poor blood to your lungs, where it unloads carbon dioxide and picks up oxygen. ... The second pump delivers oxygen-rich blood to every part of your body. Blood needing more oxygen is sent back to the heart to begin the cycle again.
Explanation:
It’s letter A
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A
It is used to represent the number of atoms in the element. H2O is 2 Hydrogen molecules and one oxygen molecule, however we don’t wright the 1.
How long ago did two species of birds share an ancestor
