Final answer:
(C) Abscess debridement. Abscess debridement is a nonsterile procedure, while the other options are sterile procedures.
Step-by-step explanation:
A nonsterile procedure refers to a medical procedure that does not require a sterile environment or the use of sterile equipment. Among the options provided, the nonsterile procedure is Abscess debridement. This procedure involves removing dead and infected tissue from an abscess, usually using local anesthesia. It does not require the same level of sterility as the other options, such as Spay (a surgical procedure to sterilize a female animal), Orthopedic surgery (a surgery that involves the musculoskeletal system), or Exploratory surgery (a surgical procedure done to investigate and diagnose a condition).