This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Upper Limb Traumatology, Subject name: Orthopaedics
[{'content': 'Which of the following is test of posterior glenohumeral instability: \nSelect and explain. \nA. Fulcrum test, B. Sulcus test, C. Jerk test, D. Crank test', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Posterior Instability (Adduction and internal rotation force) Jerk (provocative) test Posterior apprehension test Posterior clunk test Push-Pull test Anterior Instability Tests Fulcrum test Crank test Surprise test (most accurate) Jobe relocation test', 'role': 'assistant'}]