Question

 human heart is four chambered  .
    Reason : vena cava is the only artery that supplies deoxygenated blood to the                     heart    
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Answer 1

Answer:

The four-chambered heart provides an efficient solution by keeping oxygenated and non-oxygenated blood separate. The supply of oxygen to the body can also be improved by increasing how often the heart contracts.

The 4 chambered heart prevents the mixing of oxygenated blood from the lung and deoxygenated blood from the body.