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: Biochemistry
[{'content': 'Rate limiting step in pyrimidine synthesis ? \nSelect and explain. \nA. Dihydro-orotase, B. Ornithine transcarbomoylase, C. Aspaate transcarbomoylase, D. Carbamoyl phosphate synthase-I', 'role': 'user'}, {'content': "Answer: C \nExplanation: Ans. is 'c' i.e., Aspaate transcarbomoylase", 'role': 'assistant'}]