When a person is exercising, the body needs to deliver increased amounts of oxygen to the muscles. Which component of blood ensures that the muscles will receive it?

Erythrocytes, or red blood cells, carry oxygen from the lungs to the body's tissues. During exercise, they deliver oxygen to the working muscles so those muscles can produce energy. Thrombocytes help blood clot, leukocytes fight infection, and plasma is the liquid portion of blood.

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