This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Blood Vessels of Thorax, Subject name: Anatomy
[{'content': 'Internal thoracic artery is a branch of - \nSelect and explain. \nA. 1st part of subclavian artery, B. 2nd part of subclavian artery, C. 3rd part of subclavian artery, D. Thyrocervical trunk', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., 1st part of subclavian artery Ref: BDC Vol III 5th/e p. 179]Branches of subclav ian artery :-o 1st Part - Vertebral artery, internal thoracic artery, thyrocervical trunk, and on left side costocervical trunk,o 2nd Part -On right side costocervical trunk,o 3rd Part - Dorsal scapular artery.", 'role': 'assistant'}]