While Climbing to a Mount Everest Base Camp You Find

Multiple Choice

While climbing to a Mount Everest base camp you find that you have less energy to climb the higher you go.The most likely reason for this is that

A) your metabolic rate increases at higher altitudes.
B) it is harder to get rid of CO₂ from your lungs at higher altitudes.
C) there is a lower percentage of oxygen in the air at higher altitudes.
D) it is more difficult for your blood to obtain oxygen from the air at higher altitudes.
E) the partial pressure of oxygen in the air is higher at higher altitudes.