Which of the following is a sign of hypovolemia?

A weak pulse is indicative of hypovolemia, which is a condition where there is a decreased volume of blood in the body. When hypovolemia occurs, there is insufficient blood volume to maintain adequate circulation and perfusion to vital organs. This decreased volume could lead to a weak pulse as the heart struggles to pump blood effectively under reduced preload conditions.

In contrast, conditions such as a bounding pulse, elevated blood pressure, and increased urine output do not align with the typical physiological responses to hypovolemia. A bounding pulse often reflects conditions like fluid overload, while elevated blood pressure could suggest hypertension or a compensatory response in other circumstances. Increased urine output typically occurs when there is an excess of fluid, which is not compatible with hypovolemic states, where urine output tends to decrease due to reduced kidney perfusion and a compensatory mechanism aimed at conserving fluid.