Food is the answer it’s that simple appreciate this sn I really don’t know I’m sorry ...
The best way may be is going over the notes on the chapter you were doing. Or going over the chapter once or twice.
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.
