Question

How will you describe the sequence of oxygen, carbon dioxide and blood flow?

Answer 1

1. Inhale Oxygen
2. Goes to lung (bronchi - alveoli)
3. Exhale Carbon Dioxide

How to know that blood is with O2 or CO2:

Vein = Blood + CO2 = Blue
Artery = Blood + O2 = Red 

Answer 2

When You Inhale Oxygen come in it goes through trachea bronchi and lungs and blood carry oxygen to the body cells to remove carbon dioxide