This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Anatomy
[{'content': 'All of the following forms the boundaries of the lower triangular space of arm, EXCEPT? \nSelect and explain. \nA. Teres major, B. Shaft of humerus, C. Pectoralis major, D. Long head of triceps', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Boundaries of lower triangular space of arm are: medially it is bounded by long head of triceps, laterally by medial border of humerus and superiorly by teres major. Radial nerve and profunda brachii vessels are the contents of the lower triangular space.', 'role': 'assistant'}]