I think its 3. My science is really bad but ...i think i got it
The cells in the blood carry the oxygen/carbon dioxide around from different organ to another to support the whole body .Therefore it should be Muscle Cells -> Bloodstream .
Because its leaving by the nose , it must go through the windpipe before that and not the lungs(Hence the answer is not 1).If it goes through the windpipe, it must also go through the lungs because its connected.
The administrator has disabled public write access.