Smoking have life-threatening effects on a smoker's lungs. A smoker is at a high risk of lung cancer and chronic obstructive pulmonary disease. In order for a coach to explain the destructive effects of smoking on the performance of the athletes, it is best to show a diagram of the flow of the oxygen-rich blood in a non-smoker's body and then the flow of blood with less-oxygen in smoker's body. This will show the difference between the two situations clearly, and show how the airway resistance effects the performance of a person.
Hence, the answer is 'option C - Diagram the flow of oxygen-rich blood in non-smoker's body and the, diagram of flow of blood with less oxygen in smoker's body'.