Which of the following is a common indicator of dehydration?

The presence of dry mouth and fatigue is a common indicator of dehydration because these symptoms arise from the body experiencing a deficit of fluids. When the body becomes dehydrated, it struggles to maintain essential functions, leading to sensations such as dryness in the mucous membranes (like the mouth) and feelings of tiredness or fatigue due to decreased energy and efficiency in cellular processes. This is the body's way of signaling a need for more water to restore balance and support optimal functioning.

In contrast, increased energy levels would typically be associated with proper hydration and nutrition. Rapid weight gain usually indicates fluid retention or excess caloric intake rather than a state of dehydration. Bradycardia, or a slower than normal heart rate, is not a direct symptom of dehydration; instead, dehydration often leads to tachycardia, or an increased heart rate, as the body attempts to maintain blood pressure and circulation with decreased blood volume.