Final answer:
The 80-year-old diabetic client with a foot ulcer is at the greatest risk for decreased wound healing.
Step-by-step explanation:
The client at greatest risk for decreased wound healing is the 80-year-old diabetic client with a foot ulcer (option d). Diabetes can impair the body's ability to heal wounds, especially when blood sugar levels are not well controlled. High blood sugar levels can impair blood flow to the wound, decrease the function of immune cells, and delay the production of new tissue.
In addition to diabetes, the client also has an ulcer in the foot. Ulcers are open wounds that take longer to heal compared to superficial scrapes, like that of the 10-year-old postappendectomy patient (option a). The poorly nourished active 50-year-old man (option b) may have slower healing due to malnutrition, but diabetes poses a greater risk in this scenario.
The 76-year-old patient who has undergone an elective knee surgery (option c) may also have delayed wound healing due to age and the surgical procedure, but the client's diabetic condition and foot ulcer make option d the greatest risk.