This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Upper limb, Subject name: Anatomy
[{'content': 'Which of the following movement of thumb is lost in ulnar nerve injury \nSelect and explain. \nA. Opposition, B. Extension, C. Adduction, D. Abduction', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Weakness of adduction of the thumb, which may be assessed by the presence of Froment&;s sign.', 'role': 'assistant'}]