You are answering a USMLE-style medical question. Question: A 24-year-old woman presents to the emergency department with a 2-week history of a foot ulcer. She says that she punctured her foot with a rusty nail while she was playing tennis and that the puncture wound has since progressed to a non-healing ulcer. Over the last 2 days, she has also been experiencing a fever and drainage from the wound. On presentation, she is found to have a slightly fruity smelling red ulcer with purulent drainage. Probing the ulcer goes all the way down to bone. Which of the following characteristics is true of the most likely cause of this patient's symptoms? Options: A) Gram-negative bacilli B) Gram-negative diplococci C) Gram-positive cocci in chains D) Gram-positive cocci in clusters Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.