Final answer:
Pitting edema is a key indicator of fluid volume overload, as it represents the accumulation of excess water in the body tissues. The condition is marked by the skin maintaining a dimple after pressure is applied.
Step-by-step explanation:
A nurse assessing a client's hydration status should look for various signs. When evaluating for fluid volume overload, one of the key indicators is pitting edema, which is the condition where the skin maintains a dimple after being pressed. This occurs because of the accumulation of excess water in the body tissues. Therefore, the correct answer to the question is c) Pitting edema. Neither sunken eyeballs, a decrease in blood pressure, nor dark yellow urine are indicative of fluid volume overload. Instead, these signs are typically associated with dehydration or other medical conditions.