This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Injuries Around Shoulder, Subject name: Orthopaedics
[{'content': 'The most important physical sign for the diagnosis of anterior instability of the glenohumeral joint is a positive: \nSelect and explain. \nA. Apprehension sign, B. Impingement sign, C. Resisted straight arm raising sign, D. Resisted forearm supination sign', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. A. Apprehension signClassically, a patient with recurrent anterior instability or subluxation exhibits marked apprehension when the relaxed shoulder is stressed in abduction and external rotation. The impingement sign and the drop arm sign indicate disease of the rotator cuff. A positive resisted straight arm raising test (Speed's test) and a positive resisted forearm supination test (Yergason's sign) suggest pathology in the biceps tendon.", 'role': 'assistant'}]