Final answer:
Increased carbon dioxide levels in the blood lead to higher acidity (lower pH), reducing hemoglobin's affinity for oxygen and enhancing oxygen delivery to tissues during increased metabolic demands such as exercise.
Step-by-step explanation:
An increase in blood acidity is typically associated with a decrease in bicarbonate levels and an accumulation of carbon dioxide. Therefore, the correct answer is: B. Decreased carbon dioxide levels. During intense physical activity, the muscles produce carbon dioxide as a byproduct of metabolism. If the body's ability to eliminate carbon dioxide through respiration is insufficient, carbon dioxide levels in the blood can rise, leading to an increase in acidity, a condition known as acidosis. The impact on performance is significant. Acidosis can contribute to muscle fatigue, impair enzyme function, and disrupt metabolic processes. It can also affect the oxygen-carrying capacity of hemoglobin. While enhanced oxygen delivery (Option D) is generally associated with improved performance, increased acidity has the opposite effect, potentially compromising athletic performance and causing discomfort and fatigue. Maintaining proper acid-base balance is crucial for optimal physiological function during exercise.