The answer is B because viruses don't need to be fed.
Your answer is a , atoms .
Answer:haemoglobin
Explanation:
Inside the air sacs, oxygen moves across paper-thin walls to tiny blood vessels called capillaries and into your blood. A protein called haemoglobin in the red blood cells then carries the oxygen around your body.
B because it’s talking about the tree itself. Saying that it’s plants would divert it to a different plant. The cells of the wood is what makes the tree and is relevant to the question