A nurse in an emergency department is caring for an Infant who has a 2-day history of vomiting and an elevated temperature. Which of the following should the nurse recognize as the most reliable indicator of fluid loss?

A. Blood pressure can fluctuate and may not accurately reflect fluid loss in an infant, especially in early stages of dehydration. B. Respiratory rate may increase with distress but is not a direct indicator of fluid loss. C. Skin integrity can show signs of dehydration, but it is not as definitive as changes in body weight. D. Body weight is the most reliable indicator of fluid loss, as it reflects changes in fluid status directly and provides a clear measure for assessing hydration.