This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Upper Extremity, Subject name: Anatomy
A 34-year-old woman is admitted to the hospital after a car collision. Physical examination reveals a mallet finger. Which of the following conditions is expected to be present during radiographic examination? 
Select and explain. 
A. A lesion of the ulnar nerve at the distal flexor crease of the wrist, B. A separation of the extension expansion over the middle interphalangeal joint, C. Compression of the deep ulnar nerve by dislocation of the lunate bone, D. Avulsion fracture of the dorsum of the distal phalanx
D: Avulsion fracture of the dorsum of the distal phalanx
Answer: D: Avulsion fracture of the dorsum of the distal phalanx 
Explanation: Mallet finger, also known as baseball finger, is a deformity in which the finger will be permanently flexed at the distal interphalangeal joint, due to avulsion of the insertion of the extensor tendon at the distal phalanx.