B

The surgeon repeatedly gave appropriate instructions, but the patient’s own failure to obtain the prescribed wound dressings directly caused the enlargement of the wound and subsequent osteomyelitis. In malpractice law this is classic “contributory negligence” by the patient, which relieves or markedly reduces the physician’s liability, while “last clear chance” and “avoidable negligence” refer to different doctrines and no wrong prescription was given [Hudson & Moore, 2011, PMID 21094012; Buckner, Journal Med Pract Manag, PMID 12235943].