Task: Sentence Ordering
Input (English): Steps: (1) Air goes into the lungs (2) Oxygen diffuses from alveoli in the lungs to the bloodstream (3) Hemoglobin in red blood cells attaches to the oxygen (4) Red blood cells carry oxygen all around the body (5) Oxygen diffuses into cells from capillaries.  
Where does the following step fit into the given list of steps: The lungs remove oxygen from the air 
Output (English):  After step 1.