It's what carries your oxygen to the tissues from the lungs and brings waste product, carbon dioxide, away from the tissues back to the lungs.
(It; 's; what carries your oxygen to the tissues from the lungs and brings waste product, carbon dioxide, away from the tissues back to the lungs)
It
's
what carries your oxygen to the tissues from the lungs and brings waste product, carbon dioxide, away from the tissues back to the lungs