Answer:
I think that the answer A.
Explanation:
hope it helps
The Arteries carries the blood away from the Heart. And the Vein brings the blood back to heart.
Ventilation systems are needed in a <span>multicellular organism to actually obtain oxygen and give out carbon dioxide. Without this ventilation system, it would be very difficult for multicellular organisms to survive. It has been also observed that surface diffusion is not enough for a multicellular organism to breath.</span>
<span>This principle, or thought process, is that in basic sports fitness programs, all athletes training to continuously improve must always work harder an harder as their bodies become more used to their existing work out routines.</span>
R r r r d. X cc cc. Cc d. Cc. F
