The correct answer is B. Lack of Oxygen.
When there is a lack of oxygen, the body’s cells switch to anaerobic respiration, which produces lactic acid as a waste product. This is why people who exercise strenuously can experience muscle cramps and fatigue, as the muscles are not getting enough oxygen to produce energy aerobically.
A. Lack of water is not a factor in the breakdown of pyruvate into lactic acid. In fact, dehydration can actually worsen the symptoms of lactic acidosis, as it can lead to a decrease in blood flow to the muscles.
C. Lack of carbon dioxide is also not a factor in the breakdown of pyruvate into lactic acid. Carbon dioxide is a waste product of cellular respiration, and it is not involved in the production of lactic acid.
D. Lack of nitrogen is not a factor in the breakdown of pyruvate into lactic acid. Nitrogen is an essential nutrient for the body, but it is not involved in the production of lactic acid.