Teacher:In this task, you are given a paragraph, and your task is to construct a question from the given passage. Construct question in such a way that (i) it is well explained in the paragraph, (ii) the words may/may not be present in the paragraph, (iii) it should start with what/how/describe. Avoid creating a question that (i) is just relevant to one or two sentences, and (ii) not relevant to passage. 
Teacher: Now, understand the problem? Solve this instance: The human body takes a breath inward. Air is transported to the lungs. Air reaches the alveoli, the smallest air sacs in the lungs. In the alveoli, air passes into the blood within small capillaries. The gaseous oxygen in the air dissolves into the capillary blood. The dissolved oxygen is picked-up by red blood cells. The red blood cells bind the oxygen via a protein called heme. Red blood cells circulate throughout the body and reach the various tissues. Within small capillaries, the heme release the oxygen. The oxygen can then reach the cells within the tissue. 
Student:
Describe how oxygen reaches cells in the body