Which of the following is a sign of dehydration during exercise?

B. Dry mouth and dizziness are well-recognized signs of dehydration, particularly during exercise. When the body does not have enough fluids, it struggles to maintain normal physiological functions. Dry mouth occurs as saliva production decreases, leading to a sensation of thirst. Dizziness may result from decreased blood volume and blood pressure, as well as an impaired ability to deliver oxygen and nutrients to muscles and organs. These symptoms indicate that the body is in a state of dehydration, which can negatively impact performance and overall health during physical activity.

The other options do not reflect signs of dehydration. Increased energy levels and increased strength are not consistent with dehydration, as fluid loss generally leads to fatigue and reduced physical performance. Faster recovery time is also not associated with dehydration, since proper hydration is crucial for recovery and muscle repair. Thus, the presence of dry mouth and dizziness serves as a clear warning that the body needs more fluids to function optimally.