Are There Ways To Improve Blood Oxygen Levels?

Suppose that you are an athlete, and that you will be competing in an aerobic athletic event in a few months (like long-distance running). You want to increase the oxygen carrying capacity of your blood. [copy and paste the following questions into the answer-box, to answer them] 1) Explain the one major factor that determines the amount of oxygen that is in the blood (two sentences max). 2) Name three methods (2a, 2b, 2c) by which the major factor could be increased, and explain the mechanisms (two sentence for each mechanism max).