Answer:
I transfer oxygen from the atmosphere to your blood
I shrink smaller every time I take a bath. What am I?
I am a path between high natural masses; remove the first letter to get a path between man-made masses.
I am an instrument you can hear but cannot touch or see. What am I?
I have two bodies joined together as one. When standing still I run and run.
Give it food and it will live, give it water and it will die.