A. Nitrogen
B. Hydrogen
C. Carbon Dioxide
D. Argon

Submitted by: Kashif Ali Gaad

When you inhale (breathe in), air enters your lungs, and oxygen from that air moves to your blood. At the same time, carbon dioxide, a waste gas, moves from your blood to the lungs and is exhaled (breathed out). This process, called gas exchange, is essential to life.